Seachoice Brazed Non- Insulated Butt Connectors, Wire Range: #4 AWG (25-Pack) 60241 - The Home Depot
Copper Splice Cap Crimp, 14 - 4 AWG
Step-Down Tinned Butt Splice
Amazon.com: ZOOKOTO 2Pcs 4 Gauge Wire Audio Car Brass Terminal Butt Connectors Car Stereo Power or Ground Wire Splice Coupler : Electronics
Amazon.com: 10 pcs 4 AWG 4 Gauge Butt Splice Connector Pure Copper Tin Coated Marine Grade Uninsulated - by WindyNation : Industrial & Scientific
Amazon.com: OMT Wire Connector 4 Pack, 175A Wire Harness Plug Kit for 2 to 4 Gauge Cables, 12V to 36V Battery Quick Connect Disconnect Set for Car Bike ATV Winches Lifts Motors
4 Gauge (AWG) Pure Copper Cable Lug Connector Ring Terminals – Windy Nation Inc