For: King Arms SPR MK12 Mod 1 for M16/M4I got this kit for my dads ICS M4, a little gift for Fathers Day;-)
Installing it on the ICS was EASY, no major mods, just a little filing on the hop pu unit ( on the little wings) a little grinding on the gas tube( cut about 3- 5 mm) and if you get a 509 inner barrel barrel, you will have to cut about an inch off of it.
why? because the SPR mk12 mod 1 is a " M4 SNIPER" wich means a little longer than the M4 Carbine, but shorter than the M16 ( barrel lenght 509 mm).
so you can choose to get a 509 inner barrel, or stay with the stock one but the MadBull Precision Barrel for M16 http://www.airsoftgi.com/product_info.php?cPath=31_55&pr-
will give you about 15% better performance.
here are some specs, because I know I needed them and nobody had them.
barrel lenght : about 19" from hop up end
barrel lenght with flash hider: 20" from reciver to end
RAS lenght 12"
weight: unloaded, with scope : 8 lbs ( ICS M4)
final toughts: WOW
thanx ASGI !