Polaris IPLMD750-3 750-250 Mcm Non -Ul Insulated Multi-Tap Conn 3 Port (Dual Sided Entry & Mountable)
https://nsiindustries.com/product/3-port-black-mountable-pre-insulated-connector-750-mcm-1-0-awg/
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.