Both are in excellent condition and will turn your AR15 into a single shot "bolt action" for feeding extreme long range OAL .223 cartridges that can't be magazine loaded, and to disallow bolt cocking upon firing.
Bob Sled single cartridge feeder, solid Delrin "magazine" block - $25 shipped via USPS Priority.
KaliKey gas key block and charger - $60 shipped via USPS Priority.
OR, both for $80 shipped via USPS Priority!