4 Strand Tube Standard - The Most Popular - Attached to Bullskin - High Quality Rubber Tube Good For Hundred of Shots. Ships FREE via US Mail. 17*45 rubber tubing. Specification: The rubber tubing is made from the top quality latex imported from Malaysia. It's specially made for slingshot with the new formula. The 17 means the inside diameter is 1.7mm, the 45 means the overall diameter of the tube is 4.5mm. Much longer service life. Why use the small rubber tubing to make a slingshot? Because we have tested and found that the small rubber tubing can be stretched longer and creates greater initial velocity than the rough rubber tubing, so the multiple-strand small rubber tubings as showed below can be stretched to about 6.2 times of its original length and has much better performance than a single big tubing. We are an authorized importer of Dankung slingshots. Dankung is one of the worlds premier slingshot manufacturers in China. We pay for the freight from China and Ship to you FREE via First Class Mail in the USA with Delivery Confirmation. Get a second tube set for only $5 more.