Style QR Buna-N Quattro Rings, -113 Size, 5 Per Pack

Four-lobed seals like these handle reciprocating motion better than standard o-rings in most cases. The extra contact surface cuts down on the spiral twist you tend to get with round cross-section rings, and that means the seal stays seated more consistently through the stroke. For hydraulic cylinders running regular back-and-forth cycles, that added stability makes a real difference in how long the seal lasts before you start seeing seepage.