'Madbull' Ultimate 3-in-1 Hop Up Chamber Unit for M4 / M16 Series (Free Shark Hop Bucking) (MB-HOPUNIT).

Another practical innovation from MADBULL, this new metal hop-up unit / chamber has 3 functions in 1! Designed by airsoft player Brian Holt, Madbull implemented Brian's idea with the following smart features: 1. LED Tracer Unit (Optional item sold separately) Product Code: MB-LED 2. Chamber Lock (Prevents BBs from falling out when you eject magazine) 3. Easy adjustment using new design dial for more stable hop-up This set also includes a free MADBULL blue 60 degree SHARK hop-up bucking rubber. Note that the chamber lock function works via an O-ring in the BB feed tube that goes up to the firing chamber. The O-ring prevents BB's from falling out of the gun when you pull the magazine out, which is normal in a Marui type gearbox. If you find this causes any problems for you, or you prefer that the 3-4 BB's in the feed tube fall out of the gun during reloads, you can simply remove this O-ring to disable the chamber lock function. New hop-up adjustment dial stays in place and won't shift from vibration during full-auto firing, giving you more reliable and consistent hop-up than in traditional guns with slide-type hop-up adjustment lever.

For details of the product, please visit madbull official web site:

http://www.madbullairsoft.com