Bunker Kings Knuckle Butt Range The BK Knuckle Butt is the perfect combination of ultra-durable tank protection, advanced shoulder grip grooves and unique Bunker Kings style. Constructed of anti-tear Elastomer which increases durability and ease of use. Made to fit all sized tanks The Knuckle Butt’s unique design lets you quickly check the hydro date of your bottle by simply rolling the edge without having to remove the whole thing, this gets your tank approved in seconds, Bunker Kings styling is always the best part of the Knuckle Butt, designed with sucker-free graphics, straight from the slick streets of NYC!  Key Features Ultra-Durable Tank Protection One Size Fits All Awesome Sucker-Free Designs Shoulder Gripping Grooves Innovative And Unique Flat Folding Function Advanced Grip Increasing and Anti-Tear Material Quick Roll Up Date-Check Function