The RD is an 11 speed XT, specs say 33T chain wrap. I have an 11-40 cassette and a 36T chainring. I just tried it with 2 full links and it's working just fine, but there is plenty of chain to spare. I'll leave it like that and see if I get chain drops. Having a bit of slack will allow me to swap for a larger chainring if I find 36 is too small.