I get 1/2" 3 to 1 heatshrink from heatshrinktubing1 on ebay or wirecare.com as my all purpose shrink for cable making. For smaller wires, however, you may want to move to 1/4". 3 to 1 is fairly stiff so if you want flexibility, using 2 to 1 might be better. You need to determine what works best for you, especially from a sizing standpoint. If you get too large a diameter, it won't do you much good, and if you get too small, you won't be able to fit it over anything.