That's a pretty big open-ended question so here's a link to a great AK article which includes a pretty big MAK90 section at the very end... you can scroll down to it if you want, but the whole article is a great read:
AK-47 Kalashnikov Information and Pictures
And more... "SEARCH" is my friend:
Firearms 1st- Review and Discussion » The Semiautomatic AK-47 Shopper’s Guide
The SKS and AK Rifles
That last one contains the following quote:
"The Navy Seals and the Military Defense Council of Finland, both selected Norinco of China to supply Chinese type 56 AK-47 rifles, which are virtually identical (except for select-fire components) to the Norinco MAK-90, & without the MAK-90's thumbhole stock).
THAT SHOULD TELL YOU SOMETHING, as the GALIL AK's, F.E.G.'s from Hungary, Arsenal of Bulgaria, and Russian AK's were all tested against the Chinese Norinco, and the Norinco came out on top as the most rugged, and best value, despite the fact that it would have been easier for Finland and the Navy Seals to buy AK-47 variants from other Eastern European, or Russian sources.
Finally, Norinco of China, Zastava of Yugoslavia, and Valmet/Sako of Finland all use at least 1.5mm steel for their stamped receivers on their AK variants, thus eliminating the need for a "mickey-mouse" anti-trip device (band-aid that does not solve the problem of too thin of receiver) found in the trigger groups of thinner 1mm steel receivers of Warsaw-Pact AKM's."