R-338 Square O-Ring (ID: 3 1/8", CS 3/16", OD 3 1/2"), 16PK The o ring is placed into a groove to secure them in place, and then compressed between two surfaces..
R-153 Square O-Ring (ID: 3 1/2", CS 3/32", OD 3 11/16") (1 Square O-Ring) The o ring is placed into a groove to secure them in place, and then compressed between two surfaces..
.R-019 Square O-Ring (ID: 13/16", CS 1/16", OD 15/16"), 8PK The o ring is placed into a groove to secure them in place, and then compressed between two surfaces.