What are British Standard O-Ring sizes?

A common question is what are the sizing of various British Standard (BS) O-rings.

BS Numbers are a very common and easy way for identification but should you need to identify an o-ring by measuring then this conversion table below may be of assistance.

BS Number

O-Ring Size
(ID x Cross Section (mm))

Nominal Size (Inches)

ID OD Cross Section
         

BS001

0.74 x 1.02

1/32

3/32

1/32

BS002

1.07 x 1.27

3/64

9/64

3/64

BS003

1.42 x 1.52

1/16

3/16

1/16

BS004

1.78 x 1.78

5/64

13/64

1/16

BS005

2.57 x 1.78

3/32

7/32

1/16

BS006

2.90 x 1.78

1/8

1/4

1/16

BS007

3.68 x 1.78

5/32

9/32

1/16

BS008

4.47 x 1.78

3/16

5/16

1/16

BS009

5.28 x 1.78

7/32

11/32

1/16

BS010

6.07 x 1.78

1/4

3/8

1/16

BS011

7.65 x 1.78

5/16

7/16

1/16

BS012

9.25 x 1.78

3/8

1/2

1/16

BS013

10.82 x 1.78

7/16

9/16

1/16

BS014

12.42 x 1.78

1/2

5/8

1/16

BS015

14 x 1.78

9/16

11/16

1/16

BS016

15.6 x 1.78

5/8

3/4

1/16

BS017

17.17 x 1.78

11/16

13/16

1/16

BS018

18.77 x 1.78

3/4

7/8

1/16

BS019

20.35 x 1.78

13/16

15/16

1/16

BS020

21.95 x 1.78

7/8

1

1/16

BS021

23.52 x 1.78

15/16

1 1/16

1/16

BS022

25.12 x 1.78

1

1 1/8

1/16

BS023

26.7 x 1.78

1 1/16

1 3/16

1/16

BS024

28.3 x 1.78

1 1/8

1 1/4

1/16

BS025

29.87 x 1.78

1 13/16

1 5/16

1/16

BS026

31.47 x 1.78

1 1/4

1 3/8

1/16

BS027

33.05 x 1.78

1 5/16

1 7/16

1/16

BS028

34.65 x 1.78

1 3/8

1 1/2

1/16

BS029

37.82 x 1.78

1 1/2

1 5/8

1/16

BS030

41.0 x 1.78

1 5/8

1 3/4

1/16

BS031

44.17 x 1.78

1 3/4

1 7/8

1/16

BS032

47.35 x 1.78

1 7/8

2

1/16

BS033

50.52 x 1.78

2

2 1/8

1/16

BS034

53.7 x 1.78

2 1/8

2 1/4

1/16

BS035

56.87 x 1.78

2 1/4

2 3/8

1/16

BS036

60.05 x 1.78

2 3/8

2 1/2

1/16

BS037

63.22 x 1.781

2 1/2

2 5/8

1/16

BS038

66.4 x 1.78

2 5/8

2 3/4

1/16

BS039

69.57 x 1.78

2 3/4

2 7/8

1/16

BS040

72.75 x 1.78

2 7/8

3

1/16

BS041

75.92 x 1.78

3

3 1/8

1/16

BS042

82.27 x 1.78

3 1/4

3 3/8

1/16

BS043

88.62 x 1.78

3 1/2

3 5/8

1/16

BS044

94.97 x 1.78

3 3/4

3 7/8

1/16

BS045

101.32 x 1.78

4

4 1/8

1/16

BS046

107.67 x 1.78

4 1/4

4 3/8

1/16

BS047

114.02 x 1.78

4 1/2

4 5/8

1/16

BS048

120.37 x 1.78

4 3/4

4 7/8

1/16

BS049

126.72 x 1.78

5

5 1/8

1/16

BS050

133.07 x 1.78

5 1/4

5 3/8

1/16

BS102

1.25 x 2.62

1/16

1/4

3/32

BS103

2.06 x 2.62

3/32

9/32

3/32

BS104

2.85 x 2.62

1/8

5/16

3/32

BS105

3.63 x 2.62

5/32

11/32

3/32

BS106

4.42 x 2.62

3/16

3/8

3/32

BS107

5.23 x 2.62

7/32

13/32

3/32

BS108

6.02 x 2.62

1/4

7/16

3/32

BS109

7.60 x 2.62

5/16

1/2

3/32

BS110

9.20 x 2.62

3/8

9/16

3/32

BS111

10.77 x 2.62

7/16

5/8

3/32

BS112

12.37 x 2.62

1/2

11/16

3/32

BS113

13.95 x 2.62

9/16

3/4

3/32

BS114

15.55 x 2.62

5/8

13/16

3/32

BS115

17.12 x 2.62

11/16

7/8

3/32

BS116

18.72 x 2.62

3/4

15/16

3/32

BS117

20.30 x 2.62

13/16

1

3/32

BS118

21.90 x 2.62

7/8

1 1/16

3/32

BS119

23.47 x 2.62

15/16

1 1/8

3/32

BS120

25.07 x 2.62

1

1 3/16

3/32

BS121

26.65 x 2.62

1 1/16

1 1/4

3/32

BS122

28.25 x 2.62

1 1/8

1 5/16

3/32

BS123

29.82 x 2.62

1 13/16

1 3/8

3/32

BS124

31.42 x 2.62

1 1/4

1 7/16

3/32

BS125

33.0 x 2.62

1 5/16

1 1/2

3/32

BS126

34.6 x 2.62

1 3/8

1 9/16

3/32

BS127

36.17 x 2.62

1 7/16

1 5/8

3/32

BS128

37.77 x 2.62

1 1/2

1 11/16

3/32

BS129

39.35 x 2.62

1 9/16

1 3/4

3/32

BS130

40.95 x 2.62

1 5/8

1 5/8

3/32

BS131

42.52 x 2.62

1 11/16

1 3/4

3/32

BS132

44.12 x 2.62

1 3/4

1 15/16

3/32

BS133

45.7 x 2.62

1 13/16

2

3/32

BS134

47.30 x 2.62

1 7/8

2 1/16

3/32

BS135

48.90 x 2.62

1 15/16

2 1/8

3/32

BS136

50.47 x 2.62

2

2 3/16

3/32

BS137

52.07 x 2.62

2 1/16

2 1/4

3/32

BS138

53.64 x 2.62

2 1/8

2 5/16

3/32

BS139

55.25 x 2.62

2 3/16

2 3/8

3/32

BS140

56.82 x 2.62

2 1/4

2 7/16

3/32

BS141

58.42 x 2.62

2 5/16

2 1/2

3/32

BS142

59.99 x 2.62

2 3/8

2 9/16

3/32

BS143

61.60 x 2.62

2 7/16

2 5/8

3/32

BS144

63.17 x 2.62

2 1/2

2 11/16

3/32

BS145

64.77 x 2.62

2 9/16

2 3/4

3/32

BS146

66.34 x 2.62

2 5/8

2 13/16

3/32

BS147

67.95 x 2.62

2 11/16

2 7/8

3/32

BS148

69.52 x 2.62

2 3/4

2 15/16

3/32

BS149

71.12 x 2.62

2 13/16

3

3/32

BS150

72.70 x 2.62

2 7/8

3 1/16

3/32

BS151

75.87 x 2.62

3

3 3/16

3/32

BS152

82.22 x 2.62

3 1/4

3 7/16

3/32

BS153

88.57 x 2.62

3 1/2

3 11/16

3/32

BS154

94.92 x 2.62

3 3/4

3 15/16

3/32

BS155

101.27 x 2.62

4

4 3/16

3/32

BS156

107.62 x 2.62

4 1/4

4 7/16

3/32

BS157

113.97 x 2.62

4 1/2

4 11/16

3/32

BS158

120.32 x 2.62

4 3/4

4 15/16

3/32

BS159

126.67 x 2.62

5

5 3/16

3/32

BS160

133.02 x 2.62

5 1/4

5 7/16

3/32

BS161

139.37 x 2.62

5 1/2

5 11/16

3/32

BS162

145.72 x 2.62

5 3/4

5 15/16

3/32

BS163

152.07 x 2.62

6

6 3/16

3/32

BS164

158.42 x 2.62

6 1/4

6 7/16

3/32

BS165

164.77 x 2.62

6 1/2

6 11/16

3/32

BS166

171.12 x 2.62

6 3/4

6 15/16

3/32

BS167

177.47 x 2.62

7

7 3/16

3/32

BS168

183.82 x 2.62

7 1/4

7 7/16

3/32

BS169

190.17 x 2.62

7 1/2

7 11/16

3/32

BS170

196.52 x 2.62

7 3/4

7 15/16

3/32

BS171

202.87 x 2.62

8

8 3/16

3/32

BS172

209.22 x 2.62

8 1/4

8 7/16

3/32

BS173

215.57 x 2.62

8 1/2

8 11/16

3/32

BS174

221.92 x 2.62

8 3/4

8 15/16

3/32

BS175

228.27 x 2.62

9

9 3/16

3/32

BS176

234.62 x 2.62

9 1/4

9 7/16

3/32

BS177

240.97 x 2.62

9 1/2

9 11/16

3/32

BS178

247.32 x 2.62

9 3/4

9 15/16

3/32

BS201

4.34 x 3.53

3/16

7/16

1/8

BS202

5.94 x 3.53

1/4

1/2

1/8

BS203

7.52 x 3.53

5/16

9/16

1/8

BS204

9.12 x 3.53

3/8

5/8

1/8

BS205

10.69 x 3.53

7/16

11/16

1/8

BS206

12.29 x 3.53

1/2

3/4

1/8

BS207

13.87 x 3.53

9/16

13/16

1/8

BS208

15.47 x 3.53

5/8

7/8

1/8

BS209

17.04 x 3.53

11/16

15/16

1/8

BS210

18.64 x 3.53

3/4

1

1/8

BS211

20.22 x 3.53

13/16

1 1/16

1/8

BS212

21.82 x 3.53

7/8

1 1/8

1/8

BS213

23.39 x 3.53

15/16

1 3/16

1/8

BS214

24.99 x 3.53

1

1 1/4

1/8

BS215

26.57 x 3.53

1 1/16

1 5/16

1/8

BS216

28.17 x 3.53

1 1/8

1 3/8

1/8

BS217

29.74 x 3.53

1 13/16

1 7/16

1/8

BS218

31.34 x 3.53

1 1/4

1 1/2

1/8

BS219

32.92 x 3.53

1 5/16

1 9/16

1/8

BS220

34.52 x 3.53

1 3/8

1 5/8

1/8

BS221

36.09 x 3.53

1 7/16

1 11/16

1/8

BS222

37.69 x 3.53

1 1/2

1 3/4

1/8

BS223

40.87 x 3.53

1 5/8

1 7/8

1/8

BS224

44.09 x 3.53

1 3/4

2

1/8

BS225

47.22 x 3.53

1 7/8

2 1/8

1/8

BS226

50.39 x 3.53

2

2 1/4

1/8

BS227

53.57 x 3.53

2 1/8

2 3/8

1/8

BS228

56.75 x 3.53

2 1/4

2 1/2

1/8

BS229

59.92 x 3.53

2 3/8

2 5/8

1/8

BS230

63.09 x 3.53

2 1/2

2 3/4

1/8

BS231

66.27 x 3.53

2 5/8

2 7/8

1/8

BS232

69.44 x 3.53

2 3/4

3

1/8

BS233

72.62 x 3.53

2 7/8

3 1/8

1/8

BS234

75.80 x 3.53

3

3 1/4

1/8

BS235

78.97 x 3.53

3 1/8

3 3/8

1/8

BS236

82.14 x 3.53

3 1/4

3 1/2

1/8

BS237

85.32 x 3.53

3 3/8

3 5/8

1/8

BS238

88.49 x 3.53

3 1/2

3 3/4

1/8

BS239

91.67 x 3.53

3 5/8

3 7/8

1/8

BS240

94.84 x 3.53

3 3/4

4

1/8

BS241

98.02 x 3.53

3 7/8

4 1/8

1/8

BS242

101.20 x 3.53

4

4 1/4

1/8

BS243

104.37 x 3.53

4 1/8

4 3/8

1/8

BS244

107.54 x 3.53

4 1/4

4 1/2

1/8

BS245

110.72 x 3.53

4 3/8

4 5/8

1/8

BS246

113.89 x 3.53

4 1/2

4 3/4

1/8

BS247

117.07 x 3.53

4 5/8

4 7/8

1/8

BS248

120.24 x 3.53

4 3/4

5

1/8

BS249

123.42 x 3.53

4 7/8

5 1/8

1/8

BS250

126.60 x 3.53

5

5 1/4

1/8

BS251

129.77 x 3.53

5 1/8

5 3/8

1/8

BS252

132.95 x 3.53

5 1/4

5 1/2

1/8

BS253

136.12 x 3.53

5 3/8

5 5/8

1/8

BS254

139.30 x 3.53

5 1/2

5 3/4

1/8

BS255

142.47 x 3.53

5 5/8

5 7/8

1/8

BS256

145.64 x 3.53

5 3/4

6

1/8

BS257

148.82 x 3.53

5 7/8

6 1/8

1/8

BS258

152.0 x 3.53

6

6 1/4

1/8

BS259

158.34 x 3.53

6 1/4

6 1/2

1/8

BS260

164.70 x 3.53

6 1/2

6 3/4

1/8

BS261

171.04 x 3.53

6 3/4

7

1/8

BS262

177.40 x 3.53

7

7 1/4

1/8

BS263

183.74 x 3.53

7 1/4

7 1/2

1/8

BS264

190.10 x 3.53

7 1/2

7 3/4

1/8

BS265

196.44 x 3.53

7 3/4

8

1/8

BS266

202.80 x 3.53

8

7 1/4

1/8

BS267

209.14 x 3.53

8 1/4

7 1/2

1/8

BS268

215.50 x 3.53

8 1/2

7 3/4

1/8

BS269

221.84 x 3.53

8 3/4

9

1/8

BS270

228.20 x 3.53

9

7 1/4

1/8

BS271

234.55 x 3.53

9 1/4

7 1/2

1/8

BS272

240.90 x 3.53

9 1/2

7 3/4

1/8

BS273

247.25 x 3.53

9 3/4

10

1/8

BS274

253.60 x 3.53

10

10 1/4

1/8

BS275

266.29 x 3.53

10 1/2

10 3/4

1/8

BS276

278.99 x 3.53

11

11 1/4

1/8

BS277

291.69 x 3.53

11 1/2

11 3/4

1/8

BS278

304.39 x 3.53

12

12 1/4

1/8

BS279

329.79 x 3.53

13

13 1/4

1/8

BS280

355.19 x 3.53

14

14 1/4

1/8

BS281

380.59 x 3.53

15

15 1/4

1/8

BS282

405.26 x 3.53

16

16 1/4

1/8

BS283

430.66 x 3.53

17

17 1/4

1/8

BS284

456.06 x 3.53

18

18 1/4

1/8

BS309

10.47 x 5.33

7/16

7/16

3/16

BS310

12.07 x 5.33

1/2

1/2

3/16

BS311

13.64 x 5.33

9/16

9/16

3/16

BS312

15.24 x 5.33

5/8

5/8

3/16

BS313

16.82 x 5.33

11/16

11/16

3/16

BS314

18.42 x 5.33

3/4

3/4

3/16

BS315

19.99 x 5.33

13/16

13/16

3/16

BS316

21.59 x 5.33

7/8

7/8

3/16

BS317

23.17 x 5.33

15/16

15/16

3/16

BS318

24.77 x 5.33

1

1

3/16

BS319

26.34 x 5.33

1 1/16

1 1/16

3/16

BS320

27.94 x 5.33

1 1/8

1 1/8

3/16

BS321

29.52 x 5.33

1 13/16

1 3/16

3/16

BS322

31.12 x 5.33

1 1/4

1 5/8

3/16

BS323

32.69 x 5.33

1 5/16

1 11/16

3/16

BS324

34.29 x 5.33

1 3/8

1 3/4

3/16

BS325

37.47 x 5.33

1 1/2

1 7/8

3/16

BS326

40.64 x 5.33

1 5/8

2

3/16

BS327

43.82 x 5.33

1 3/4

2 1/8

3/16

BS328

46.99 x 5.33

1 7/8

2 1/4

3/16

BS329

50.17 x 5.33

2

2 3/8

3/16

BS330

53.34 x 5.33

2 1/8

2 1/2

3/16

BS331

56.52 x 5.33

2 1/4

2 5/8

3/16

BS332

59.69 x 5.33

2 3/8

2 3/4

3/16

BS333

62.87 x 5.33

2 1/2

2 7/8

3/16

BS334

66.64 x 5.33

2 5/8

3

3/16

BS335

69.22 x 5.33

2 3/4

3 1/8

3/16

BS336

72.39 x 5.33

2 7/8

3 1/4

3/16

BS337

75.57 x 5.33

3

3 3/8

3/16

BS338

78.74 x 5.33

3 1/8

3 1/2

3/16

BS339

81.92 x 5.33

3 1/4

3 5/8

3/16

BS340

85.09 x 5.33

3 3/8

3 3/4

3/16

BS341

88.27 x 5.33

3 1/2

3 7/8

3/16

BS342

91.44 x 5.33

3 5/8

4

3/16

BS343

94.62 x 5.33

3 3/4

4 1/8

3/16

BS344

97.79 x 5.33

3 7/8

4 1/4

3/16

BS345

100.97 x 5.33

4

4 3/8

3/16

BS346

104.14 x 5.33

4 1/8

4 1/2

3/16

BS347

107.32 x 5.33

4 1/4

4 5/8

3/16

BS348

110.49 x 5.33

4 3/8

4 3/4

3/16

BS349

113.67 x 5.33

4 1/2

4 7/8

3/16

BS350

116.84 x 5.33

4 5/8

5

3/16

BS351

120.02 x 5.33

4 3/4

5 1/8

3/16

BS352

123.19 x 5.33

4 7/8

5 1/4

3/16

BS353

126.37 x 5.33

5

5 3/8

3/16

BS354

129.54 x 5.33

5 1/8

5 1/2

3/16

BS355

132.72 x 5.33

5 1/4

5 5/8

3/16

BS356

135.89 x 5.33

5 3/8

5 3/4

3/16

BS357

139.07 x 5.33

5 1/2

5 7/8

3/16

BS358

142.24 x 5.33

5 5/8

6

3/16

BS359

145.42 x 5.33

5 3/4

6 1/8

3/16

BS360

148.59 x 5.33

5 7/8

6 1/4

3/16

BS361

151.77 x 5.33

6

6 3/8

3/16

BS362

158.12 x 5.33

6 1/4

6 5/8

3/16

BS363

164.47 x 5.33

6 1/2

6 7/8

3/16

BS364

170.82 x 5.33

4 3/4

7 1/8

3/16

BS365

177.17 x 5.33

7

7 3/8

3/16

BS366

183.52 x 5.33

7 1/4

7 5/8

3/16

BS367

189.87 x 5.33

7 1/2

7 7/8

3/16

BS368

196.22 x 5.33

7 3/4

8 1/8

3/16

BS369

202.57 x 5.33

8

8 3/8

3/16

BS370

208.92 x 5.33

8 1/4

8 5/8

3/16

BS371

215.27 x 5.33

8 1/2

8 7/8

3/16

BS372

221.62 x 5.33

8 3/4

9 1/8

3/16

BS373

227.97 x 5.33

9

9 3/8

3/16

BS374

234.32 x 5.33

9 1/4

9 5/8

3/16

BS375

240.67 x 5.33

9 1/2

9 7/8

3/16

BS376

247.02 x 5.33

9 3/4

10 1/8

3/16

BS377

253.37 x 5.33

10

10 3/8

3/16

BS378

266.07 x 5.33

10 1/2

10 7/8

3/16

BS379

278.77 x 5.33

11

11 3/8

3/16

BS380

291.47 x 5.33

11 1/2

11 7/8

3/16

BS381

304.17 x 5.33

12

12 3/8

3/16

BS382

329.57 x 5.33

13

13 3/8

3/16

BS383

354.97 x 5.33

14

14 3/8

3/16

BS384

380.37 x 5.33

15

15 3/8

3/16

BS385

405.26 x 5.33

16

16 3/8

3/16

BS386

430.66 x 5.33

17

17 3/8

3/16

BS387

456.06 x 5.33

18

18 3/8

3/16

BS388

481.38 x 5.33

19

19 3/8

3/16

BS389

506.78 x 5.33

20

20 3/8

3/16

BS390

532.18 x 5.33

21

21 3/8

3/16

BS391

557.58 x 5.33

22

22 3/8

3/16

BS392

582.68 x 5.33

23

23 3/8

3/16

BS393

608.08 x 5.33

24

24 3/8

3/16

BS394

633.48 x 5.33

25

25 3/8

3/16

BS395

658.88 x 5.33

26

26 3/8

3/16

BS425

113.67 x 7

4 1/2

5

1/4

BS426

116.84 x 7

4 5/8

5 1/8

1/4

BS427

120.02 x 7

4 3/4

5 1/4

1/4

BS428

123.19 x 7

4 7/8

5 3/8

1/4

BS429

126.37 x 7

5

5 1/2

1/4

BS430

129.54 x 7

5 1/8

5 5/8

1/4

BS431

132.72 x 7

5 1/4

5 3/4

1/4

BS432

135.89 x 7

5 3/8

5 7/8

1/4

BS433

139.07 x 7

5 1/2

6

1/4

BS434

142.24 x 7

5 5/8

6 1/8

1/4

BS435

145.42 x 7

5 3/4

6 1/4

1/4

BS436

148.59 x 7

5 7/8

6 3/8

1/4

BS437

151.77 x 7

6

6 1/2

1/4

BS438

158.12 x 7

6 1/4

6 3/4

1/4

BS439

164.47 x 7

6 1/2

7

1/4

BS440

170.82 x 7

4 3/4

7 1/4

1/4

BS441

177.17 x 7

7

7 1/2

1/4

BS442

183.52 x 7

7 1/4

7 3/4

1/4

BS443

189.87 x 7

7 1/2

8

1/4

BS444

196.22 x 7

7 3/4

8 1/4

1/4

BS445

202.57 x 7

8

8 1/2

1/4

BS446

215.27 x 7

8 1/2

9

1/4

BS447

227.97 x 7

9

9 1/2

1/4

BS448

240.67 x 7

9 1/2

10

1/4

BS449

253.37 x 7

10

10 1/2

1/4

BS450

266.07 x 7

10 1/2

11

1/4

BS451

278..77 x 7

11

11 1/2

1/4

BS452

291.47 x 7

11 1/2

12

1/4

BS453

304.17 x 7

12

12 1/2

1/4

BS454

316.87 x 7

12 1/2

13

1/4

BS455

329.57 x 7

13

13 1/2

1/4

BS456

342.27 x 7

13 1/2

14

1/4

BS457

354.97 x 7

14

14 1/2

1/4

BS458

367.67 x 7

14 1/2

15

1/4

BS459

380.37 x 7

15

15 1/2

1/4

BS460

393.07 x 7

15 1/2

16

1/4

BS461

405.26 x 7

16

16 1/2

1/4

BS462

417.96 x 7

16 1/2

17

1/4

BS463

430.66 x 7

17

17 1/2

1/4

BS464

443.36 x 7

17 1/2

18

1/4

BS465

456.06 x 7

18

18 1/2

1/4

BS466

468.76 x 7

18 1/2

19

1/4

BS467

481.46 x 7

19

19 1/2

1/4

BS468

494.16 x 7

19 1/2

20

1/4

BS469

506.86 x 7

20

20 1/2

1/4

BS470

532.26 x 7

21

21 1/2

1/4

BS471

557.66 x 7

22

22 1/2

1/4

BS472

582.68 x 7

23

23 1/2

1/4

BS473

608.08 x 7

24

24 1/2

1/4

BS474

633.48 x 7

25

25 1/2

1/4

BS475

658.88 x 7

26

26 1/2

1/4

BS901

4.7 x 1.42

 

 

 

BS902

6.02 x 1.63

 

 

 

BS903

7.65 x 1.63

 

 

 

BS904

8.92 x 1.83

 

 

 

BS905

10.72 x 1.83

 

 

 

BS906

11.90 x 1.98

 

 

 

BS907

13.46 x 2.08

 

 

 

BS908

16.36 x 2.21

 

 

 

BS909

17.93 x 2.46

 

 

 

BS910

19.18 x 2.46

 

 

 

BS911

21.92 x 2.95

 

 

 

BS912

23.47 x 2.95

 

 

 

BS913

25.04 x 2.95

 

 

 

BS914

26.61 x 2.95

 

 

 

BS916

29.74 x 2.95

 

 

 

BS918

34.42 x 2.95

 

 

 

BS920

37.47 x 3

 

 

 

BS924

43.69 x 3.00

 

 

 

BS928

53.09 x 3.00

 

 

 

BS932

59.36 x 3.00

 

 

 

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