Hi-Tech Seals, Inc. Back-up Ring BUM

Back-up rings are plastic or rubber rings used to prevent the O-ring from entering the clearance gap. When high pressures are exerted on the O-ring its soft rubber material can be forced into the clearance gap caused the O-ring to extrude. The hard back-up ring material will keep the O-ring material from flowing into the gap which will prevent premature failure.