Crosstak AR-15/AR-10 Modular Maintenance Kit - This modular maintenance kit firmly holds your uppers and lowers in place when maintenance is needed. The modular blocks have nylon set screws to adjust for precise fit in each magwell. The base fits AR-15 And AR-10. Includes: AR-15/AR-10 Modular Base Block AR-15 Lower Receiver Block AR-10 Lower Receiver Block AR Pin Driver Pull Pins And Hardware