Includes extended magazine spring. Easy to install and to remove for cleaning. Lightweight and durable. Features: Adds +5 capacity on 9mm Adds +4 capacity on .40 cal Fits standard capacity GLOCK 9mm & .40 magazines 3-piece design is easy to reassemble without damaging the mag body Additional power spring provided ZEV Technologies will not ship any of these items to individuals living within the state of California. Please Note: Basepads are only compatible with 17 round magazines.