If we're gonna list upgrades
ARS 3G Piston head
Tokyo Marui piston body
ARS Cylinder head /w Sorbo
Pakayama Craft Air Nozzle
ARS high spin spring guide
Prometheus M110 spring
Prometheus NEO STRIKE hop-up chamber
Prometheus 6.03 Tightbore
ARS Airseal hop-up rubber
Shredder's Concave Spacer