A pair of plastic shoulder stocks, also known as butt plates. These will fit 7 oz CO2 tanks and the very popular 13 Cubic Inch Compressed Air tanks used on many air powered markers. The ID is 2.00" and tapers down for a snug fit. Made by Allen Paintball Products of Ohio. They have been serving the paintball industry since 1987. They are known for heavy duty products. Not some cheap imported piece of junk. Tank not included. MADE IN USA FREE SHIPPING via USPS.