Outer barrel 4-piece AEG set made by XT. Great quality, aluminium, 14mm CCW thread. 

Ensure you use some grease on the threads, AEG head doesn't come with grubscrew.

Specifications:
AEG head (1.75 Inches)
1 Inch extension
2 Inch extension
5 Inches extension
Colour: Black
Total Weight: 250g
Thread Direction: 14mm - CCW