In stock at RedWolf Airsoft for US$417.00 and they give you a comparison between the AEG and GBB versions... "LMT, Lewis Machine and Tool Company. The MRP has a one piece upper receiver for ARs that allows the shooter to change the barrel length in seconds. It features a free-floating barrel, that reduces over-heating and increase the accuracy of the weapon on the real steel.

It also extends the barrel life, easy-to-access/clean design. Made from high quality Aluminum Die-Casting. This metal body features the LMT logos, and realistic body markings, as well as a unique LMT serial code machine stamped onto the body. It runs great out of the box with a decent rate of fire even on an 7.4v LiPo.

Features include:

• Full metal One Piece Railed Upper Receiver
• Full metal Lower Receiver, LMT style
• Thick One Piece Outer Barrel
• All metal standard G&P quality gearbox with M120 Motor
• Polymer Grip with Metal Motor Heatsink
• Standard flash hider 14mm CW
• QD Front and rear iron fully adjustable iron sights
• 7 positions for QD sling mounting along the entire gun
• 2 QD sling mounts included
• 3 low profile rail cover strips included
• 1 short vertical grip with storage included
• Adjustable 5 position collapsible stock with storage and rubber butt pad
• Fits Standard AEG M4/M16 magazines
• Adjustable metal hop-up unit
• ~363mm length inner barrel
• Deans Large T-Plug inside stock tube for LiPo Battery"