I wrote Blackhawk, heres their response:
Good morning, a lot of customers are expiring difficulties with the glock 21 sf weapons and holster.BlackHawk Products Group has specific holsters and instructions concerning the holster.I have included that information additionally many dealers / distributors are not aware of the glock situation.
SERPA Update for the Glock 21SF
Just in case, your customer’s are not aware, there are actually 2 different versions of the Glock 21SF on the market. Each one requires a different SERPA model to function properly.
One 21SF comes with a standard rail and fits in the SERPA holsters with size indicator "13", like the 430513BK-R, the 410013BK-R, and the 44H113BK-R.
The other 21SF comes with a deeper rail. The Glock packaging refers to it as the "1913 Rail". The holsters that fit these guns have the size indicator "26". Examples are the 430526BK-R and the 44H026BK-R.
Remember, standard rail = 13, and the 1913 rail = 26!
I hope that this helps.
Thank you
Dwyane Taylor
Customer Service
1-800-694-5263 ext3264
BlackHawk Products Group
6160 Commander Parkway
Norfolk, VA. 23502
[email protected]