1) Remove factory basepad and retainer plate.2) Remove magazine spring and slide factory follower down to base of magazine so that the load assist pin can be removed from the follower. NOTE: you will not use the load assist pin with the +1 follower.
3) Remove factory follower.
4) Insert HiCap follower into the magazine body.
5) Insert magazine spring into magazine body.
6) Compress spring with retainer plate into magazine body and slide on the basepad.
FN 502 Tactical Magazine Follower
* Due to the nature of this item and international regulations (ITAR) we can not sell to anyone that is not in the United States. All international orders will be canceled. To place an international order, the order must be placed through an exporter. Contact an exporter HERE
** This item CAN NOT be shipped to California
*** Verify your local and state laws for any restrictions before installing these parts. It is the users responsibility to verify any legal conflict with the use of these parts.
works great even works on the ten round mags. 
Not exactly how I thought it would work.