Originally Posted by c_jit

Mine is a Magpul MIAD.
First you need a 5/32 wrench to remove the factory stock.


Then you will find 2 springs (undone the grip screw slowly and be careful as they will pop out at the same time)
the front one is the safety retention pin spring and a blue one for lower pin retention spring.


Mine is a Magpul MIAD kit. But I use only a small back strap as the other two larger back strap will leave a gap on the back end where the back strap meet the frame.



A small bob of epoxy glue and cotton ball is used to seal the back end of the grip where the blue spring will reside.


I retain the factory 5/32 in mine becaues Magpul grip screw is a normal slot head and does not seem to be well made as the factory one.


This is how it look now with a MFI's barrel shroud and Magpul furnitures.