American Electrical and DigiKey offer many types of insulated, non-insulated, twin wire, and assortments of wire ferrules. Wire ferrules are a tin plated copper tube (with or without an insulation sleeve) that are mechanically crimped to the end of a conductor to secure the strands. Crimping the wire ferrule to the conductor ensures that strands do not splay, increases conductivity, and reduces resistivity while improving the overall integrity of the connection.