O-Ring Kit, Assorted Sizes

An o-ring kit is a boxed assortment of the sizes most often needed in maintenance work, held in a compartmented case so that a size can be identified and drawn without measuring loose stock. The rings themselves are ordinary o-rings and are governed by the same size and material rules as loose stock.

Kits are built on one of two size systems and the distinction matters more than the piece count. An inch kit follows the AS568 dash-number series; a metric kit follows the free metric sizes that ISO 3601-1 treats in clause 6.3 as non-standard sizes. The two do not interchange, and fitting a near-miss metric ring into an AS568 gland gives the wrong squeeze.

Almost all general-purpose kits are nitrile, which suits mineral hydraulic oil, water and air but is not resistant to weathering and ozone and is limited to about +100 °C. A kit is therefore a convenience for routine repairs, not a substitute for selecting the correct compound on a duty that involves steam, phosphate-ester fluid, aromatics or temperatures beyond the nitrile range.

When ordering, state whether the inch (AS568) or the metric series is wanted, the elastomer and hardness, and the range of cross-sections required. Piece count and the exact size list vary between suppliers and should be confirmed against the kit actually offered.