As part of their annual pre-SHOT Show announcements, Magpul has involved the TMAG 20 AR/M4 GEN M3, a 20-round capacity version of their Transparent magazine technology.
Molded from a durable translucent material with an olive drab hue, it provides shooters the ability to visibly verify various ammunition types and the current round count. Featuring ribbed front and rear straps for improved purchase during magazine changes, the sides are left smooth to enhance visibility.
Due to the shorter length, the 20 rounders lack the high visibility spring and round count markings of the 30-round variant.
https://magpul.com/tmag-20-ar-m4-gen-m3.html
