Daniel Defense is releasing their SLiM rails as an individual item. The rail uses Key Mod and is free-floating. It comes in 12 or 15 inches.
Price is $279(MSRP)
Daniel Defense is having a giveaway
http://danieldefense.com/registertowin/
Aimpoint Micro Mount is made for Micro T,H, and R optics and gives absolute co-witness or 1/3 co-witness with spacer.
Price is $79
From:
Daniel Defense,
Guns.com Gear Scout