3M CIR-21A Connector , 2, 1 AWG stranded, O.D. 0.64 in (16,2 mm), 10 per case
3M CIR Series Repair Connectors - Product Selection Guide (PDF 7.8 K)
3M™ Lugs and Connectors, 2015 Electrical Products Catalog - Catalog (PDF 2.1 MB)
3M™ Splices, 2015 Electrical Products Catalog - Catalog (PDF 11.7 MB)
This connector has 5451R splice body and a 0.63 in (16 mm) O.D. This connector is to be used with molded rubber splice kits.