Hookooekooriderwrote a review of Castelli Nano XT Gloves - Men's on December 13, 2015
Familiarity: I've used it once or twice and have initial impressions
Fit: Runs small
I wear size Large in most gloves. The fingers and width of the palm fit like a Large, but the thumb length is shorter than it should be given the finger length. The gloves fit tight, as they should. Also, in size Large, their stock is the 2014 model (i.e., the 2nd and 4th photos from the left), so call them to see if they have the 2015 model (the 1st and 2nd photos on the left) in your size if that's what you want.
I also ran the gloves under running water. The back of the glove totally sheds water. The palm of the glove does absorb water, but only on the surface, so your hand remains dry. Water will get through the seams, but this is at a slow rate, so if you're riding in light rain for shorter durations, your hand should stay fairly dry.