V7 Titanium QD End Plate and Castle Nut: both available separately or together in combo pack:
https://www.vertexops.com/V7_Titanium_Combo_p/v7-combo-ti.htm
https://www.vsevenweaponsystems.com/collections/lower-parts/products/v-seven-titanium-combo-pack
V7 Ultra Light Super Aluminum QD End Plate and Castle nut Combo Pack- 65% lighter than mil spec steel:
https://www.vertexops.com/V7_AR15_Combo_p/v7-combo.htm