The Pro MAg magazine is compatible with your Glock 21/30. It is constructed of DuPont Zytel polymer with full length steel internal insert, injection molded mag follower and mag spring formed from chrome silicone wire. Made in the USA.
ProMag GLKA11 Standard 13rd 40 S&W Compatible w/Glock 23/27 Black DuPont Zytel Polymer
$17.00