NSI R12-6V 12-10 Awg Vinyl Insulated Ring #6 Stud, 50 Per Pack
https://nsiindustries.com/product/nsi-r12-6v-12-10-awg-vinyl-insulated-ring-6-stud-50-per-pack/
Tin-plated Copper Ring Terminal with Vinyl Insulation for wire termination in applications with #6 Stud and 12-10 AWG