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Japanese O-rings - JIS B2401

The use of substitute O-rings in underwater equipment should, in general, be avoided.  If substitution is necessary, the following issues should be considered:
torus_k Material type is selected for resistance to damage, chemical attack and UV light.  Types used in underwater engineering applications are usually Nitrile-butadiene (NBR), Silicone, or Buna.
torus_b Material hardness is important.  Too soft and the O-ring will extrude under pressure, causing catastrophic failure.  Too hard and the seal will be stiff and prone to abrasion damage.  Underwater housing door, port and control O-rings usually have Shore hardness in the 60 to 75 range.
torus_r Japanese O-rings do not have exact substitutes from the standard European and American inch and metric size ranges.

Given below are the specifications for Japanese Industry Standard (JIS) B2401 series O-rings.
torus_k Once a size has been found, note that a complete spec. also includes material type and hardness.  For example, the O-ring for a Nikonos plug is P9, the material is NBR or Silicone, and the Shore hardness (Sh) is 60-70. 
torus_k It is not unusual for manufacturers to use non-standard (specially manufactured) sizes.
O-ring dimensions

All dimensions in mm


d = 1.5 ±0.1 D (±0.15)
S 2 1.5
S 3 2.5
S 4 3.5
S 5 4.5
S 6 5.5
S 7 6.5
S 8 7.5
S 9 8.5
S 10 9.5
S 11.2 10.7
S 12 11.5
S 12.5 12.0
S 14 13.5
S 15 14.5
S 16 15.5
S 18 17.5
S 20 19.5
S 22 21.5



d = 1.9 ±0.07 D (±0.12)
P 2 1.8
P 3 2.8
P 4 3.8
P 5 4.8
P 6 5.8
P 7 6.8
P 8 7.8
P 9 8.8
P 10 9.8



d = 2.0 ±0.1 D (±0.15)
S 22.4 21.9
S 24 23.5
S 25 24.5
S 26 25.5
S 28 27.5
S 29 28.5
S 30 29.5
S 31.5 31.0
S 32 31.5
S 34 33.5
S 35 34.5
S 35.5 35.0
S 36 35.5
S 38 37.5
S 39 38.5
S 40 39.5

d = 2.0 ±0.1 D (±0.25)
S 42 41.5
S 44 43.5
S 45 44.5
S 46 45.5
S 48 47.5
S 50 49.5
S 53 52.5
S 55 54.5
S 56 55.5
S 60 59.5
S 63 62.5
S 65 64.5
S 67 66.5
S 70 69.5

d = 2.0 ±0.1 D (±0.4)
S 71 70.5
S 75 74.5
S 80 79.5
S 85 84.5
S 90 89.5
S 95 94.5
S 100 99.5
S 105 104.5
S 110 109.5
S 112 111.5
S 115 114.5
S 120 119.5
S 125 124.5

d = 2.0 ±0.1 D (±0.6)
S 130 129.5
S 132 131.5
S 135 134.5
S 140 139.5
S 145 144.5
S 150 149.5
S 155 154.5
S 160 159.5
S 165 164.5
S 170 169.5
S 175 174.5
S 180 179.5

d = 2.0 ±0.1 D (±0.8)
S 185 184.5
S 190 189.5
S 195 194.5
S 200 199.5
S 205 204.5
S 210 209.5
S 215 214.5
S 220 219.5
S 225 224.5
S 230 229.5
S 235 234.5
S 240 239.5
S 245 244.5
S 250 249.5
S 255 254.5
S 260 259.5
S 265 264.5
S 270 269.5
S 275 274.5
S 280 279.5
S 285 284.5
S 290 289.5
S 295 294.5
S 300 299.5



d = 2.4 ±0.07 D (±0.12)
P 10A 9.8
P 11 10.8
P 11.2 11.0
P 12 11.8
P 12.5 12.3
P 14 13.8
P 15 14.8
P 16 15.8
P 18 17.8

d = 2.4 ±0.07 D (±0.15)
P 20 19.8
P 21 20.8
P 22 21.8



d = 3.1 ±0.1 D (±0.15)
G 25 24.4
G 30 29.4
G 35 34.4
G 40 39.4

d = 3.1 ±0.1 D (±0.25)
G 45 44.4
G 50 49.4
G 52 51.4
G 55 54.4
G 58 57.4
G 60 59.4
G 62 61.4
G 63 62.4
G 64 63.4
G 65 64.4
G 67 66.4
G 70 69.4

d = 3.1 ±0.1 D (±0.40)
G 72 71.4
G 75 74.4
G 80 79.4
G 85 84.4
G 90 89.4
G 95 94.4
G 100 99.4
G 105 104.4
G 110 109.4
G 115 114.4
G 120 119.4
G 125 124.4

d = 3.1 ±0.1 D (±0.60)
G 130 129.4
G 135 134.4
G 140 139.4
G 145 144.4
Gs 150 149.3
Gs 155 154.3
Gs 160 159.3
Gs 165 164.3
Gs 170 169.3
Gs 175 174.3
Gs 180 179.3

d = 3.1 ±0.1 D (±0.80)
Gs 185 184.3
Gs 190 189.3
Gs 195 194.3
Gs 200 199.3
Gs 205 204.3
Gs 210 209.3
Gs 215 214.3
Gs 220 219.3
Gs 225 224.3
Gs 230 229.3
Gs 235 234.3
Gs 240 239.3
Gs 245 244.3
Gs 250 249.3
Gs 255 254.3
Gs 260 259.3
Gs 265 264.3
Gs 270 269.3
Gs 275 274.3
Gs 280 279.3
Gs 285 284.3
Gs 290 289.3
Gs 295 294.3
Gs 300 299.3

d = 3.1 ±0.12 D (±1.20)
Gs 305 304.3
Gs 310 309.3
Gs 315 314.3
Gs 320 319.3
Gs 325 324.3
Gs 330 329.3
Gs 335 334.3
Gs 340 339.3
Gs 345 344.3
Gs 350 349.3
Gs 355 354.3
Gs 360 359.3
Gs 365 364.3
Gs 370 369.3
Gs 375 374.3
Gs 380 379.3
Gs 385 384.3
Gs 390 389.3
Gs 395 394.3
Gs 400 399.3

d = 3.1 ±0.12 D (±1.50)
Gs 405 404.3
Gs 410 409.3
Gs 415 414.3
Gs 420 419.3
Gs 425 424.3
Gs 430 429.3
Gs 435 434.3
Gs 440 439.3
Gs 445 444.3
Gs 450 449.3
Gs 455 454.3
Gs 460 459.3
Gs 465 464.3
Gs 470 469.3
Gs 475 474.3
Gs 480 479.3
Gs 485 484.3
Gs 490 489.3
Gs 495 494.3
Gs 500 499.3



d = 3.5 ±0.1 D (±0.15)
P 22A 21.7
P 22.4 22.1
P 24 23.7
P 25 24.7
P 25.5 25.2
P 26 25.7
P 28 27.7
P 29 28.7
P 29.5 29.2
P 30 29.7
P 31 30.7
P 31.5 31.2
P 32 31.7
P 34 33.7
P 35 34.7
P 35.5 35.2
P 36 35.7
P 38 37.7
P 39 38.7
P 40 39.7

d = 3.5 ±0.1 D (±0.25)
P 41 40.7
P 42 41.7
P 44 43.7
P 45 44.7
P 46 45.7
P 48 47.7
P 49 48.7
P 50 49.7



d = 5.7 ±0.15 D (±0.25)
P 48A 47.6
P 50A 49.6
P 52 51.6
P 53 52.6
P 55 54.6
P 56 55.6
P 58 57.6
P 60 59.6
P 62 61.6
P 63 62.6
P 65 64.6
P 67 66.6
P 70 69.6

d = 5.7 ±0.15 D (±0.4)
P 71 70.6
P 75 74.6
P 80 79.6
P 85 84.6
P 90 89.6
P 95 94.6
P 100 99.6
P 102 101.6
P 105 104.6
P 110 109.6
P 112 111.6
P 115 114.6
P 120 119.6
P 125 124.6

d = 5.7 ±0.15 D (±0.6)
P 130 129.6
P 132 131.6
P 135 134.6
P 140 139.6
P 145 144.6
P 150 149.6

d = 5.7 ±0.15 D (±0.60)
G 150 149.3
G 155 154.3
G 160 159.3
G 165 164.3
G 170 169.3
G 175 174.3
G 180 179.3

d = 5.7 ±0.15 D (±0.80)
G 185 184.3
G 190 189.3
G 195 194.3
G 200 199.3
G 210 204.3
G 215 214.3
G 220 219.3
G 225 224.3
G 230 229.3
G 235 234.3
G 240 239.3
G 245 244.3
G 250 249.3
G 255 254.3
G 260 259.3
G 265 264.3
G 270 269.3
G 275 274.3
G 280 279.3
G 285 284.3
G 290 289.3
G 295 294.3
G 300 299.3

d = 5.7 ±0.15 D (±1.00)
G 305 304.3
G 310 309.3
G 315 314.3
G 320 319.3
G 325 324.3
G 330 329.3
G 335 334.3
G 340 339.3
G 345 344.3
G 350 349.3
G 355 354.3
G 360 359.3
G 365 364.3
G 370 369.3
G 375 374.3
G 380 379.3
G 385 384.3
G 390 389.3
G 395 394.3
G 400 399.3

d = 5.7 ±0.15 D (±1.20)
G 405 404.3
G 410 409.3
G 415 414.3
G 420 419.3
G 425 424.3
G 430 429.3
G 435 434.3
G 440 439.3
G 445 444.3
G 450 449.3
G 455 454.3
G 460 459.3
G 465 464.3
G 470 469.3
G 475 474.3
G 480 479.3
G 485 484.3
G 490 489.3
G 495 494.3
G 500 499.3
G 505 504.3

d = 5.7 ±0.15 D (±1.60)
G 510 509.3
G 515 514.3
G 520 519.3
G 525 524.3
G 530 529.3
G 535 534.3
G 540 539.3
G 545 544.3
G 550 549.3
G 555 554.3
G 560 559.3
G 565 564.3
G 570 569.3
G 575 574.3
G 580 579.3
G 585 584.3
G 590 589.3
G 595 594.3
G 600 599.3



d = 8.4 ±0.15 D (±0.6)
P 150A 149.5
P 155 154.5
P 160 159.5
P 165 164.5
P 170 169.5
P 175 174.5
P 180 179.5

d = 8.4 ±0.15 D (±0.8)
P 185 184.5
P 190 189.5
P 195 194.5
P 200 199.5
P 205 204.5
P 209 208.5
P 210 209.5
P 215 214.5
P 220 219.5
P 225 224.5
P 230 229.5
P 235 234.5
P 240 239.5
P 245 244.5
P 250 249.5
P 255 254.5
P 260 259.5
P 265 264.5
P 270 269.5
P 275 274.5
P 280 279.5
P 285 284.5
P 290 289.5
P 295 294.5
P 300 299.5

d = 8.4 ±0.15 D (±1.0)
P 305 304.5
P 310 309.5
P 315 314.5
P 320 319.5
P 325 324.5
P 330 329.5
P 335 334.5
P 340 339.5
P 345 344.5
P 350 349.5
P 355 354.5
P 360 359.5
P 365 364.5
P 370 369.5
P 375 374.5
P 380 379.5
P 385 384.5
P 390 389.5
P 395 394.5
P 400 399.5

d = 8.4 ±0.15 D (±1.2)
P 405 404.5
P 410 409.5
P 415 414.5
P 420 419.5
P 425 424.5
P 430 429.5
P 435 434.5
P 440 439.5
P 445 444.5
P 450 449.5
P 455 454.5
P 460 459.5
P 465 464.5
P 470 469.5
P 475 474.5
P 480 479.5
P 485 484.5
P 490 489.5
P 495 494.5
P 500 499.5

d = 8.4 ±0.15 D (±1.6)
P 505 504.5
P 510 509.5
P 515 514.5
P 520 519.5
P 525 524.5
P 530 529.5
P 535 534.5
P 540 539.5
P 545 544.5
P 550 549.5
P 555 554.5
P 560 559.5
P 565 564.5
P 570 569.5
P 575 574.5
P 580 579.5
P 585 584.5
P 590 589.5
P 595 594.5
P 600 599.5

sq_k