Polaris IPLMD3/0-5 Black Mountable Dual-Side Entry Insulated Multi-Tap Connector, 5-Port, 3/0 AWG-6 AWG
https://www.nsiindustries.com/product/5-port-black-mountable-pre-insulated-connector-3-0-6-gauge/
Polaris Black Multi-Tap Mountable Connectors form secure connections between multiple conductors with a rounded design and UV-resistant insulation coating. Installs with a hex key and torque wrench, with no need for cover and taping.