Spikes STU5435R2S Complete Upper 5.56x45mm NATO 16" Black Phosphate/Midlength Barrel, 7075-T6 Aluminum Black Receiver, 12" SAR3 Free-Floating Handguard for AR-15 $788.40
Aero Precision APAR308506AC M5E1 Enhanced Receiver 308 Win 7075-T6 Aluminum Flat Dark Earth Cerakote Receiver for M5 Platform $239.99
Spikes SFT50M4 Flat Top Stripped Upper Multi-Caliber 7075-T6 Aluminum Black Anodized Receiver for M4 Platform $103.50