Hard plastic. You just take off the HK94 front handguard and the SD shroud slips on. Tight fit, but it just feels weird when you hold it because it is hard plastic. The finish isn't perfect when you look at it closely, but it looks good in pictures. Not bad for $43.00
The M3 conversion? If so, I was in talks with the seller on a trade, but not sure if that'll go through as the thread currently shows as sold pending funds. :-( I was all for the trade, but maybe next time.