This heat shrink has a 3:1 ratio and is great for heavier duty jobs (most heat shrink shrinks with a 2:1 ratio). The inside seals nicely with the cables and makes wire connections that are VERY strong. The box with the separators is flimsy and the separators keep coming out of their slots, but I don't really care about the box. They provide a good mixture of sizes. I would definitely purchase these again.