Henning Group's Blueline Glock 17/34/19X/45 Magazine Extension increases capacity to 21 + 1. Comes with extra power magazine spring. Glock 17, 17L, 34, 19X,45 - 9mm Standard Length Mags. Designed in collaboration with a current SWAT Operator and US Army Veteran, our Magazine Extensions offer:           

Confident magazine indexing through our patent pending design.

Improved grip support for shooters with larger hands.

Basepad allows for an effortless strip with the knife-edge of the support hand on malfunctions or stuck magazines.

The kit comes with magazine extension and a longer magazine spring.
U.S. Patent 9,772,151