Metric Nitrile O-Rings are one of the simplest, yet most engineered, precise and useful seal designs ever developed. This assortment of O-rings features metrically-sized parts measuring 3mm in total width with parts running 20mm thru 30mm in inner diameter. O-rings in this assortment are made of high-strength Nitrile (Buna-N) rubber. O-rings are ideal for myriad applications. DIY projects, plumbing services, and contracting work are made easier with Hillman O-rings. Full assortments of #56263 contain eight (8) refills comprised of Hillman item numbers #56264 - #56271.