8 Strand Tube For Skillful Shooter Shooting Big Ammo - Attached to Bullskin - High Quality Rubber Tube Good For Hundreds of Shots. It's made of 8-strand 2040 rubber tubing. It's specially made for western shooters , the length is 17cm . The 20 means the inside diameter is 2mm, the 40 means the overall diameter of the tube is 4mm. 4 strands of 2040 rubber tubing attaching with a pouch of bull skin tightly sewed. It's perfect setup for people have average arm strength to take small game hunt with 5/16, 3/8 and 1/2 diameter steel ball ammo. Length: 17cm Full draw: about 93cm. Pull force: 16KG. Ships FREE via US Mail First Class Mail. Get a second tube set for only $5.95 more.