the SGS-5 is hard to find parts for here are some parts that are high quality and fit without modification you can buy you stocks at airsoft extreme they actually have them seems to be the only place left The B&T folding stock fits perfect no mods required. The Mp5 ICS tactical rail set works like a champ no mods required fits right high quality part with bottom handle magazines can only be found at scottsdale arizona gun club there pricey but well made. Airsoft Atlanta has some nice sight rails but there sold out of everything else.

The sightmark holographic reflex sight for 30 dollars works like a charm and fits right on. Instead of searching the net and comeing up empty with all parts sold out everywhere you can find them where I have them listed at and they fit the GSG with no modification.