Same as TomTac from Helmetworld
http://www.helmetworld.co.uk/toy-aeg-8mm-full-gearbox-m4-v2-front-wire-qd-quick-release-tokyo-marui-32950-p.asp
think with discount NC15 it is about same price shipped - most likely may have a m120 spring in there
but nice easy way of getting gun going again
I bought a couple from helmetworld on ebay and though not skirmished yet am impressed with them
and seem to be good quality and at least I don't get clobbered with custo,s charge risk from o/seas
you could look at HW and maybe consider a new inner if ya balls up your long-short chopping on Raider
(soz to add to shopping list but a possible consideration getting cheap tomtac 300mm barrel too)
mind you think ak2m4 does these type boxes and has a cheaper inner barrel at about 300mm
even sells stuff on fleabay too but drop him a pm and he might cut a deal for ya
yup I have spent way way too much and still looking to buy more crap but missus is doing her crunch
so best i ease off for a while - well a week or so maybe