What is a Lower Parts Kit? A Lower Parts Kit (LPK) is a collection of the small parts that are needed to finish a lower receiver and make it fully functioning. What parts come in a lower parts kit? Most LPK’s come with detents, take-down pins, selector, bolt catch, and more. At Delta Team Tactical, we have a variety of LPKs in stock. Choose from LPKs with different pistol grips. We also have LPKs in a variety of colors like black, purple, red, and more. Shop our LPKs to get started finishing your AR-15 lower!