Soakers No. 5293 by Free Vintage Crochet
I could be wrong, but this looks like one large triangle that is folded together into a neat diaper cover. It also looks like a mindless pattern for you to enjoy.
As for materials, the pattern calls for a baby yarn and a No. 3 bone hook.
If you enjoyed this free crochet pattern you might also enjoy more designs made available on Free Vintage Crochet.