Shooter vault is Good. But if you want a glock 21 get the SF version (small frame) because the 21 is huge for a handgun and unless you are shack it will be really uncomfortable with the sf it just makes the grip smaller but doesn't take away from anything.
The 21 is not that big. The SF doesn't make a big difference.
But thats just my opinion.
Theirs always the 26 though...