Can I modify the 10s to hold 12? How are they "blocked"? They appear identical from the outside.
What is the difference between 10 round and 12 round P11 magazines?
2!

The difference is what's on the inside. Most likely a different spring allowing more rounds with the same tension.
The followers are diffrent it is the same mag body. From what I understand the 12rd follower has a higher chance of tilting. I do not have a link handy but the follower can be modified. WWW.ktog.org try searching there I think you will find the answer.
Originally Posted By gundummy:
Don't forget,
Your P11 will also accept S&W 12rd mags (469 & 669) as well as standard 15rd M59 (second generation) mags. KT also sells an adapter sleeve that slides over the longer mag body giving you a longer grip.
this is correct