LanTac USA LLC SF AR-15 Forged Builder Set, Anodized Finish, Black, Includes Upper/Lower Receiver and 6.75 Spada M-LOK Rail with Mounting Hardware 01-RV-BSET-6-SF Lantac AR-15 builder set includes an upper and lower receiver along with an M-LOK handguard. Their forged receiver set is packed with 'above milspec' features, making it an ideal choice for shooters seeking an upgraded configuration while maintaining a traditional look. The lower receiver has a spot face cut to the takedown area, enabling easier removal of the rear pin. The magwell is internally flared, allowing for quicker and more precise magazine seating during high-stress reloads.