Sure Plug Gen 4-5 Laser Engraved Skull - Designed for Glock 17, 19, 22, 23, 31, 32, 34, and 35. Aid in guiding the Magazine into the Magazine Well Flush fit to eliminate the possibility of snagging on the open cavity stops dirt and debris from entering the backstrap channel Made in the USA using reinforced, chemical resistent polymer material. Permanent Laser Engraving. NOTE: This grip plug will NOT install on a Gen 4 that is using any of the additional backstraps.