This kit includes a complete upper receiver/barrel assembly, allowing Mil-Spec 5.56mm AR-style rifles to be retrofitted to HK’s piston and pusher rod system. This system utilizes a piston and a pusher rod in place of the gas tube normally found in AR15/M16/M4-style rifles. This closed system virtually eliminates the malfunctions that are common in direct-impingement gas systems, since hot carbon fouling and waste gasses are not propelled into the receiver area to operate the action. This is the same key feature critical to the success of the HK416 used by elite military and law enforcement customers. Upper will ship in HK Soft case. 

The MR556 A4 Upper kit includes
1. Complete MR556 upper receiver/barrel assembly, barrel, upper receiver with forward assist, extended
charging handle and free-floating slimline handguard.
2. Complete MR556 bolt group assembly
3. HK proprietary buffer and action spring

Contrary to claim , no Multi tool or HK lock are/is provided with this kit from HK USA. 

All sale are final, this Upper kit is non returnable under any circumstance . All kits are inspected By HK before shipping to us , and we do general inspection before shipping to you, and pictures of the exact upper will be texted before shipping .