These are perfect for XC, not as light as some silicone/foam style grips but exponentially more comfortable. The one down side is I can only wrap my thumb and pointer finger all the way around the grip (the wing blocks my other fingers) so for that reason i wouldnt put these on a bike designed to tackle nasty downhillish stuff. But for the xc rides nothing beats it.
i have the large grips as i like the thicker grip. (note the size isnt width or how big the wing is, its the diameter of the grip)