I have some, the hammock bit poppers out which the MC Smart nappy doesn't. The outer is a lovely cotton jersey and rib cotton leg cuffs. The pouch/hammock holds in the wee and poo and you don't get wicking.
You can stuff them with anything - I used mf cloths with a liner. I can't recall if they do their own washable inserts. There disposable inserts are flushable, but you have to tear them up and swish them with a stick (provided with the nappies!) so they break down. They claim with the flush insert to have least environmental impact of any nappy.
The weeny pouch pants that lollipop used to do and bg flip are similar. BG flip dispoable inserts are not flushable, and not sure about mc ones. I have two friend who tried mc smart nappies, one loved them, one hated them as they always leaked
g diapers do up at the back which is quie cute