I am having some spring issues on 2/3 mags that I have put the +5 extensions on and I am looking for replacement springs. I called Arrendondo but they said they don't have any replacements to sell and that they shouldn't have worn out this quickly(less than 6 months and maybe 200 rounds through each). After searching around I found some ISMI +10% 12 coils that say they are universal but the glock 21 is not listed on the package per CPWSA and no response from ISMI directly. What is in there currently is a 12 coil spring but I am not sure if what works for 9mm/40 also works on the 45acp. Any help is greatly appreciated.