Customized and Upgraded products will need additional 2 weeks to proceed. And once upgrade process started, it won't able to refund.
Customize Option:
FPS Option (FPS 400 or 300)
Upgraded Inner Barel and Hop-Up Rubber 
 
Features:
Realistic blowback design
Removable USGI stype handle
Classic round handguard
Full steel outer barrel
Full length fixed polymer stock
 
Infornmation:
Model: M16A3
Materials: Steel, Zine Alloy, Nylon, Rubber
Length: 1100mm
Weight: 3200g (7.20 pounds)
Barrel: 510mm inner barrel
Power Source: Green Gas
Action: Semi / Auto
Ammo Type: 6mm airsoft BBs
Ammo Capacity: 20-round full-size metal magazine
FPS: 400
Bunker Tech Upgrades
Maple leaf gbb 6.02mm Inner Barrel
Maple leaf  High Accuracy Hop-up Bucking- Internal Parts Adjust
All function checks, to avoid common tolerance issues.
BB weight for optimal performance: 0.36 gram