Evike.com's Matt goes over the various variants of the A&K Cybergun FN Herstal M249 Middleweight LMGs for airsoft use... "The A&K M249 'Middleweight' series falls in between the Standard M249's and the M249 Featherweight by shedding weight in key areas to reduce each gun by several pounds. Middleweight M249's still retain A&K M249 gearboxes keeping them compatible with all A&K M249 compatible gearbox parts. All Middleweight M249's feature a high strength polymer receiver, dust cover, handguard, heat shield and gas block along with aluminum outer barrel, steel carry handle and steel folding bipod."