The original Magblock 10/30 MCL (Magazine Capacity Limiter) for Magpul 30 round Pmags in .223/5.56mm. This block will replace the lower spring attachment point or locking plate and convert a 30 round magazine to hold only 10 rounds. The Pmag dust covers will still fit when loaded and magazines can be loaded with the bolt closed. Does not affect reliability or magazine function. No increase in spring pressure which would reduce spring life. Compatable with original Pmags, Gen M2 Pmags, Magpul HK G36, and Magpul Emags. ***These will not work in Gen M3 Pmags.***