Porter Cable Models 333, 334, and 340 Canister O-ring, 897558 Replacement. Condition is New. Stops your canister from blowing off from worn O-ring! Seals and connects the adapter to dust canister on PC models 333, 334, and 340 orbital sanders. Early model sanders require 1 0-ring, later models require 2. Adjust order quantity accordingly. Quality USA made. Free shipping!