If you send a complete upper which includes a freefloat rails system/Keymod/MLOK/MCMR/DD/KAC, etc., which needs to be disassembled and then reassembled, a handguard/rail system installed, you need to select this service. This service does not include installation of new/swapped FSBs onto undrilled barrels. If your upper has a pinned/welded muzzle device you need to add that service which will destroy the device. We do not remove pressed-in/pinned barrels as used in HKs and AKs etc.. We will NOT attempt to install or remove any Chinese parts. We DO NOT take apart and reassemble LWRC uppers.