[Zfurlong]

didnt have the ics spring release, but i have had the release system on another brand (cant remember which one offhand, might have been a g&g one, but again, idk offhand, was years ago), for the most part, the release system should be contained within the gearbox itself. meaning you should only need to have to look at knob compatibility as well as ensuring you have the appropriate knob that is long enough as well as the return spring for the knob. that being said, you may need to mod the upper in order for the knob to fit the receiver properly as well as engage the release system on the gearbox properly. but remember, the more moving parts, the higher the chance of something breaking.

feel free to pm me if you have any further questions