The British Standard BS4518 is a metric standard that defines both the o-ring and hardware dimensions for rod, piston, face and trapped grooves.
The nominal hardware dimensions around which it operates are defined in millimeters.
| BS4518 Size | ID (mm) | ID Tol' (+/- mm) | CS (mm) | CS Tol' (mm) | ID (inch) | ID Tol' (+/- inch) | CS (inch) | CS Tol' (inch) |
|---|
| BS4518 -0031-16 |
3.1 |
0.15 |
1.6 |
0.08 |
0.122 |
0.006 |
0.063 |
0.003 |
| BS4518 -0041-16 |
4.1 |
0.161 |
| BS4518 -0051-16 |
5.1 |
0.201 |
| BS4518 -0061-16 |
6.1 |
0.240 |
| BS4518 -0071-16 |
7.1 |
0.280 |
| BS4518 -0081-16 |
8.1 |
0.319 |
| BS4518 -0091-16 |
9.1 |
0.358 |
| BS4518 -0101-16 |
10.1 |
0.2 |
0.398 |
0.008 |
| BS4518 -0111-16 |
11.1 |
0.437 |
| BS4518 -0121-16 |
12.1 |
0.476 |
| BS4518 -0131-16 |
13.1 |
0.516 |
| BS4518 -0141-16 |
14.1 |
0.555 |
| BS4518 -0151-16 |
15.1 |
0.594 |
| BS4518 -0161-16 |
16.1 |
0.634 |
| BS4518 -0171-16 |
17.1 |
0.673 |
| BS4518 -0181-16 |
18.1 |
0.25 |
0.713 |
0.010 |
| BS4518 -0191-16 |
19.1 |
0.752 |
| BS4518 -0221-16 |
22.1 |
0.870 |
| BS4518 -0251-16 |
25.1 |
0.988 |
| BS4518 -0271-16 |
27.1 |
1.067 |
| BS4518 -0291-16 |
29.1 |
1.146 |
| BS4518 -0321-16 |
32.1 |
0.3 |
1.264 |
0.012 |
| BS4518 -0351-16 |
35.1 |
1.382 |
| BS4518 -0371-16 |
37.1 |
1.461 |
| BS4518 -0036-24 |
3.6 |
0.15 |
2.4 |
0.142 |
0.006 |
0.094 |
| BS4518 -0046-24 |
4.6 |
0.181 |
| BS4518 -0056-24 |
5.6 |
0.220 |
| BS4518 -0066-24 |
6.6 |
0.260 |
| BS4518 -0076-24 |
7.6 |
0.299 |
| BS4518 -0086-24 |
8.6 |
0.339 |
| BS4518 -0096-24 |
9.6 |
0.378 |
| BS4518 -0106-24 |
10.6 |
0.2 |
0.417 |
0.008 |
| BS4518 -0116-24 |
11.6 |
0.457 |
| BS4518 -0126-24 |
12.6 |
0.496 |
| BS4518 -0136-24 |
13.6 |
0.535 |
| BS4518 -0146-24 |
14.6 |
0.575 |
| BS4518 -0156-24 |
15.6 |
0.614 |
| BS4518 -0166-24 |
16.6 |
0.654 |
| BS4518 -0176-24 |
17.6 |
0.693 |
| BS4518 -0186-24 |
18.6 |
0.25 |
0.732 |
0.010 |
| BS4518 -0196-24 |
19.6 |
0.772 |
| BS4518 -0206-24 |
20.6 |
0.811 |
| BS4518 -0216-24 |
21.6 |
0.850 |
| BS4518 -0246-24 |
24.6 |
0.969 |
| BS4518 -0276-24 |
27.6 |
1.087 |
| BS4518 -0296-24 |
29.6 |
1.165 |
| BS4518 -0316-24 |
31.6 |
0.3 |
1.244 |
0.012 |
| BS4518 -0346-24 |
34.6 |
1.362 |
| BS4518 -0356-24 |
35.6 |
1.402 |
| BS4518 -0376-24 |
37.6 |
1.480 |
| BS4518 -0396-24 |
39.6 |
1.559 |
| BS4518 -0416-24 |
41.6 |
1.638 |
| BS4518 -0446-24 |
44.6 |
1.756 |
| BS4518 -0456-24 |
45.6 |
1.795 |
| BS4518 -0476-24 |
47.6 |
1.874 |
| BS4518 -0496-24 |
49.6 |
1.953 |
| BS4518 -0516-24 |
51.6 |
0.4 |
2.031 |
0.016 |
| BS4518 -0546-24 |
54.6 |
2.150 |
| BS4518 -0556-24 |
55.6 |
2.189 |
| BS4518 -0576-24 |
57.6 |
2.268 |
| BS4518 -0586-24 |
58.6 |
2.307 |
| BS4518 -0596-24 |
59.6 |
2.346 |
| BS4518 -0616-24 |
61.6 |
2.425 |
| BS4518 -0626-24 |
62.6 |
2.465 |
| BS4518 -0646-24 |
64.6 |
2.543 |
| BS4518 -0676-24 |
67.6 |
2.661 |
| BS4518 -0696-24 |
69.6 |
2.740 |
| BS4518 -0195-30 |
19.5 |
0.25 |
3 |
0.1 |
0.768 |
0.010 |
0.118 |
0.004 |
| BS4518 -0215-30 |
21.5 |
0.846 |
| BS4518 -0225-30 |
22.5 |
0.886 |
| BS4518 -0245-30 |
24.5 |
0.965 |
| BS4518 -0255-30 |
25.5 |
1.004 |
| BS4518 -0265-30 |
26.5 |
1.043 |
| BS4518 -0275-30 |
27.5 |
1.083 |
| BS4518 -0295-30 |
29.5 |
1.161 |
| BS4518 -0315-30 |
31.5 |
0.3 |
1.240 |
0.012 |
| BS4518 -0325-30 |
32.5 |
1.280 |
| BS4518 -0345-30 |
34.5 |
1.358 |
| BS4518 -0355-30 |
35.5 |
1.398 |
| BS4518 -0365-30 |
36.5 |
1.437 |
| BS4518 -0375-30 |
37.5 |
1.476 |
| BS4518 -0395-30 |
39.5 |
1.555 |
| BS4518 -0415-30 |
41.5 |
1.634 |
| BS4518 -0425-30 |
42.5 |
1.673 |
| BS4518 -0445-30 |
44.5 |
1.752 |
| BS4518 -0495-30 |
49.5 |
1.949 |
| BS4518 -0545-30 |
54.5 |
0.4 |
2.146 |
0.016 |
| BS4518 -0555-30 |
55.5 |
2.185 |
| BS4518 -0575-30 |
57.5 |
2.264 |
| BS4518 -0595-30 |
59.5 |
2.343 |
| BS4518 -0625-30 |
62.5 |
2.461 |
| BS4518 -0645-30 |
64.5 |
2.539 |
| BS4518 -0695-30 |
69.5 |
2.736 |
| BS4518 -0745-30 |
74.5 |
2.933 |
| BS4518 -0795-30 |
79.5 |
3.130 |
| BS4518 -0845-30 |
84.5 |
0.5 |
3.327 |
0.020 |
| BS4518 -0895-30 |
89.5 |
3.524 |
| BS4518 -0945-30 |
94.5 |
3.720 |
| BS4518 -0995-30 |
99.5 |
3.917 |
| BS4518 -1045-30 |
104.5 |
4.114 |
| BS4518 -1095-30 |
109.5 |
4.311 |
| BS4518 -1145-30 |
114.5 |
4.508 |
| BS4518 -1195-30 |
119.5 |
4.705 |
| BS4518 -1245-30 |
124.5 |
0.6 |
4.902 |
0.024 |
| BS4518 -1295-30 |
129.5 |
5.098 |
| BS4518 -1345-30 |
134.5 |
5.295 |
| BS4518 -1395-30 |
139.5 |
5.492 |
| BS4518 -1445-30 |
144.5 |
5.689 |
| BS4518 -1495-30 |
149.5 |
5.886 |
| BS4518 -1545-30 |
154.5 |
6.083 |
| BS4518 -1595-30 |
159.5 |
6.280 |
| BS4518 -1645-30 |
164.5 |
6.476 |
| BS4518 -1695-30 |
169.5 |
6.673 |
| BS4518 -1745-30 |
174.5 |
6.870 |
| BS4518 -1795-30 |
179.5 |
7.067 |
| BS4518 -1845-30 |
184.5 |
0.8 |
7.264 |
0.031 |
| BS4518 -1895-30 |
189.5 |
7.461 |
| BS4518 -1945-30 |
194.5 |
7.657 |
| BS4518 -1995-30 |
199.5 |
7.854 |
| BS4518 -2095-30 |
209.5 |
8.248 |
| BS4518 -2195-30 |
219.5 |
8.642 |
| BS4518 -2295-30 |
229.5 |
9.035 |
| BS4518 -2395-30 |
239.5 |
9.429 |
| BS4518 -2445-30 |
244.5 |
9.626 |
| BS4518 -2495-30 |
249.5 |
9.823 |
| BS4518 -0443-57 |
44.3 |
0.3 |
5.7 |
0.12 |
1.744 |
0.012 |
0.224 |
0.005 |
| BS4518 -0453-57 |
45.3 |
1.783 |
| BS4518 -0493-57 |
49.3 |
1.941 |
| BS4518 -0523-57 |
52.3 |
0.4 |
2.059 |
0.016 |
| BS4518 -0543-57 |
54.3 |
2.138 |
| BS4518 -0553-57 |
55.3 |
2.177 |
| BS4518 -0593-57 |
59.3 |
2.335 |
| BS4518 -0623-57 |
62.3 |
2.453 |
| BS4518 -0643-57 |
64.3 |
2.531 |
| BS4518 -0693-57 |
69.3 |
2.728 |
| BS4518 -0743-57 |
74.3 |
2.925 |
| BS4518 -0793-57 |
79.3 |
3.122 |
| BS4518 -0843-57 |
84.3 |
0.5 |
3.319 |
0.020 |
| BS4518 -0893-57 |
89.3 |
3.516 |
| BS4518 -0943-57 |
94.3 |
3.713 |
| BS4518 -0993-57 |
99.3 |
3.909 |
| BS4518 -1043-57 |
104.3 |
4.106 |
| BS4518 -1093-57 |
109.3 |
4.303 |
| BS4518 -1143-57 |
114.3 |
4.500 |
| BS4518 -1193-57 |
119.3 |
4.697 |
| BS4518 -1243-57 |
124.3 |
0.6 |
4.894 |
0.024 |
| BS4518 -1293-57 |
129.3 |
5.091 |
| BS4518 -1343-57 |
134.3 |
5.287 |
| BS4518 -1393-57 |
139.3 |
5.484 |
| BS4518 -1443-57 |
144.3 |
5.681 |
| BS4518 -1493-57 |
149.3 |
5.878 |
| BS4518 -1543-57 |
154.3 |
6.075 |
| BS4518 -1593-57 |
159.3 |
6.272 |
| BS4518 -1643-57 |
164.3 |
6.469 |
| BS4518 -1693-57 |
169.3 |
6.665 |
| BS4518 -1743-57 |
174.3 |
6.862 |
| BS4518 -1793-57 |
179.3 |
7.059 |
| BS4518 -1843-57 |
184.3 |
0.8 |
7.256 |
0.031 |
| BS4518 -1893-57 |
189.3 |
7.453 |
| BS4518 -1943-57 |
194.3 |
7.650 |
| BS4518 -1993-57 |
199.3 |
7.846 |
| BS4518 -2093-57 |
209.3 |
8.240 |
| BS4518 -2193-57 |
219.3 |
8.634 |
| BS4518 -2293-57 |
229.3 |
9.028 |
| BS4518 -2393-57 |
239.3 |
9.421 |
| BS4518 -2493-57 |
249.3 |
9.815 |
| BS4518 -2593-57 |
259.3 |
1 |
10.209 |
0.039 |
| BS4518 -2693-57 |
269.3 |
10.602 |
| BS4518 -2793-57 |
279.3 |
10.996 |
| BS4518 -2893-57 |
289.3 |
11.390 |
| BS4518 -2993-57 |
299.3 |
11.783 |
| BS4518 -3093-57 |
309.3 |
1.5 |
12.177 |
0.059 |
| BS4518 -3193-57 |
319.3 |
12.571 |
| BS4518 -3393-57 |
339.3 |
13.358 |
| BS4518 -3593-57 |
359.3 |
14.146 |
| BS4518 -3793-57 |
379.3 |
14.933 |
| BS4518 -3893-57 |
389.3 |
15.327 |
| BS4518 -3993-57 |
399.3 |
15.720 |
| BS4518 -4193-57 |
419.3 |
2 |
16.508 |
0.079 |
| BS4518 -4393-57 |
439.3 |
17.295 |
| BS4518 -4593-57 |
459.3 |
18.083 |
| BS4518 -4793-57 |
479.3 |
18.870 |
| BS4518 -4893-57 |
489.3 |
19.264 |
| BS4518 -4993-57 |
499.3 |
19.657 |
| BS4518 -1441-84 |
144.1 |
0.6 |
8.4 |
0.15 |
5.673 |
0.024 |
0.331 |
0.006 |
| BS4518 -1491-84 |
149.1 |
5.870 |
| BS4518 -1541-84 |
154.1 |
6.067 |
| BS4518 -1591-84 |
159.1 |
6.264 |
| BS4518 -1641-84 |
164.1 |
6.461 |
| BS4518 -1691-84 |
169.1 |
6.657 |
| BS4518 -1741-84 |
174.1 |
6.854 |
| BS4518 -1791-84 |
179.1 |
7.051 |
| BS4518 -1841-84 |
184.1 |
0.8 |
7.248 |
0.031 |
| BS4518 -1891-84 |
189.1 |
7.445 |
| BS4518 -1941-84 |
194.1 |
7.642 |
| BS4518 -1991-84 |
199.1 |
7.839 |
| BS4518 -2041-84 |
204.1 |
8.035 |
| BS4518 -2091-84 |
209.1 |
8.232 |
| BS4518 -2191-84 |
219.1 |
8.626 |
| BS4518 -2291-84 |
229.1 |
9.020 |
| BS4518 -2341-84 |
234.1 |
9.217 |
| BS4518 -2391-84 |
239.1 |
9.413 |
| BS4518 -2491-84 |
249.1 |
9.807 |