Ultra lightweight fiberglass reinforced polymer receiver Freefloat quad rail handguard w/ suppressor Nylon fiber furniture Metal barrel assembly, flash hider, charging handle, and sling swivels ESA quick spring change system allows the spring to be changed without the need to disassemble your gun Rotary type hopup with 6.03mm tight bore barrel 380 fps spring pre-installed from factory, optional 310 fps (M90) spring included to reduce muzzle velocity Specna Arms meets the expectations of clients by presenting the CORE line of products - an exceptional series of replicas that introduces a new quality to the market. An attractive price in combination with an innovative spring change system as well as high-quality materials make this replica suitable for beginners and seasoned airsoft players alike. The receiver, stock slide, handguard and a SF stock that holds the battery, as well as the pistol grip, were made from nylon reinforced polymer. Remaining components such as the barrel, flash hider, enlarged charging handle and tactical sling swivels were made of metal (parts made of steel include the screws, pins, shell ejection window and mock bolt carrier). The receiver bears markings and a serial number. The replica's parts fit very well together and the User will not experience any loose spots between the lower and upper receiver. The use of a light polymer receiver allowed for a reduced weight, which makes it very suitable for dynamic games or long-lasting mil-sims. What's more, fiberglass reinforcement makes the receiver also more durable than polymer and metal receivers.