eHobbyAsia have sent over details of the Hephaestus custom T21 GBB they are stocking:
Hephaestus Custom – Project T (Completed GBB, Black)
Overview:
-Semi / Full Auto Shooting mode
-Built on GHK Gas BlowBack system.
-All custom parts are made from CNC machining.
-Polymer Body
-380mm Metal Outer Barrel With 45mm Flash Hider
-Flip-Up Front Sight and slide folding Rear sight
-40 rounds 6mm BB loading capacity GHK M4 Gas Magazine
-CNC machined aluminum bolt carrier, bolt catch, trigger box and outer barrel.
-CNC machined steel QD swivel socket, chamber base and other internal parts.
-Loading nozzle, fire control parts and Hop-Up system from GHK G5 GBB.
-Adjustable hop-up system
Reference link:
hhttp://shop.ehobbyasia.com/hephaestus-custom-project-t-completed-gbb-black.html
