This is a Spike's Tactical Lower Parts Kit known as the 308, model SLPKX15.
This kit is designed to be used with your Jack10 or Livewire set. To complete the lower you will want to also purchase a buffer tube assembly" stock" and trigger group of your choice. Proudly made in the USA.
Features:
Safety Selector, Detent, Spring
Magazine Catch, Spring, Billet Mag Button
Buffer Retainer Spring and Plunger
Pro Grip