Rubber Tubing made from natural latex, what is it? Natural latex rubber tubing has been given many names. Some people call it surgical tubing, exercise or fitness tube, gum rubber tubing, and dipped tubing as well as speargun bands and slingshot bands. Others may simply refer to it as "stretchy tubing". Natural Latex Rubber Tubing made by AR AR RUBBER''''S "Continuous Dip Process" creates a superior natural latex rubber tubing. The physical properties are better, the quality higher and the colors more vibrant than product manufactured from dry natural or synthetic materials. In addition, AR AR RUBBER''''s tubing has only 50 micrograms or less of water-extractable protein per gram. This is important since proteins in natural rubber can cause severe allergic reactions in those individuals who are allergic to the types of protein found in natural rubber. This is known as the "latex allergy". No other rubber tubing can claim to have lower protein levels. HOW TO DETERMINE TUBING SIZES Calculation Methods: O.D. (Outside Diameter) = Inside Diameter+Wall+Wall I.D. (Inside Diameter) = O.D.(Outside Diameter)-Wall-Wall Wall Thickness = (O.D. - I.D.)/2 Standard Tolerances: Inside Diameter: 1/64 inch on sizes up to and including 3/8 inch. Proportionately greater on larger sizes. Wall Thickness: 1/32 and 3/64 inch walls .007 inch. 1/16 inch and 5/64 inch walls 0.010 inch. 3/32 inch and 1/8 inch walls 0.015 inch. Tubing with walls greater than 1/8 inch walls are gauged by the O.D..