3M CIR-21 Connector , 2, 1 AWG stranded, O.D. 0.64 in (16,2 mm), 10 per case
This connector has 5411R splice body and a 0.63 in (16 mm) O.D. This connector is to be used with molded rubber splice kits.
The 3M™ Connector CIR-21 is an extra long connector that is used to bridge gaps up to six inches when a piece of damaged cable is removed. They can be used with copper or aluminum conductors.