The Knuckle Butt gives you is the perfection combination of tank protection, shoulder grip unique style thanks to various artist made designs. Constructed of anti-tear elastomer to increase durability and longevity. The Knuckle Butt’s unique design lets you quickly check the hydro date of your bottle and get your tank approved in seconds without having to remove the Knuckle Butt. Just roll it back for inspection. Increase your precision and performance in style.