O-Ring Standard
BS 4518 O-Rings — UK Standard O-Ring Manufacturer India
FITCO manufactures BS 4518 O-Rings across all five metric cross-section bands — 1.6mm, 2.4mm, 3.0mm, 5.7mm and 8.4mm — in NBR, FKM, EPDM, HNBR, Silicone and FFKM. BS 4518 is the British Standard for metric O-Rings and is not dimensionally equivalent to ISO 3601 or AS568 despite using millimetre sizing.
BS 4518 Cross-Section Series
| CS | Typical ID Range | Application |
|---|---|---|
| 1.6 mm | 3.1–37.1 mm | Small bore static sealing |
| 2.4 mm | 3.6–69.6 mm | General purpose |
| 3.0 mm | 19.5–249.5 mm | Medium bore sealing |
| 5.7 mm | 44.3–499.3 mm | Large bore sealing |
| 8.4 mm | 144.1–249.1 mm | Large bore high-pressure |
BS 4518 uses its own distinct ID ladder within each CS band — do not cross-reference directly to ISO 3601 or metric series without checking the dimension table. Send your BS 4518 reference number for an exact confirmation.
Send O-Ring Requirement
Send your BS 4518 reference, compound and quantity — FITCO will confirm size and price.