Thumler's Tumblers R-3 Retainer Rings ( 3 Pack) For 3lb Tumbler Barrels Thumler's A-R1, A-R2, Model-T and MP-1 Retainer ring (set of 3) Has Greater Flexibility and Abrasion Resistance Than Natural Rubber These Rings have a 15 Year Shelf Life! They Stay Pliable Down To -20 F