Only modification is on the hi cap with a spray painted “2” on it. The hi cap holds 250 rnds and the lo caps hold 45 each. The adapter itself can take standard mp5 and mp5 straight mags too. I really liked it but now the adapter won’t fit into my new m4 because there’s a little lip in it’s magwell. But this adapter will fit into any other standard m4/m16 mag wells