The supplied internal diameter of this green/yellow 2:1 heat shrink is 20 mm, the recovered internal diameter is 10 mm, and the wall thickness after recovery is 0.56 mm (±0.10). The purpose of our heat shrink sleeves is to create a tight, weatherproof seal. High-quality Polyolefin is used to make the heat shrink tubes, which tightly shrink around cables, wires, and hoses to provide environmental sealing and protection from moisture and abrasion. Heat tubing is ideal for protecting cables from adverse conditions and marking them for identification and organization in electrical systems and circuits. 1 x 20mm Yellow Green Heat Shrink Tube, 1m, is included in the kit.