Solder Sleeves are small, hollow pieces of heat shrinkable tubing that have rings of solder incorporated into them. As they are heated, the tubing shrinks making a mechanical bond between the wires inserted into them.?At the same time,?the solder melts forming an electrical connection, securely splicing wires together. Coming in a variety of diameters and lengths with special features such as environmental resistances and pre-installed lead wires, solder sleeves are suitable for a wide range of wire sizes and applications.