On our shop scale the medium comes in at 1,290 grams, which is pretty impressive. For reference, one of the lightest helmets out there is an Airoh, which claims 950 grams as its lightest (XS), and Bell claims 1,450 for the Moto-9 Flex. I wore a large and the fit, to be kind, is weird. I would say it has an oval-ish shape and the crown of the helmet fit comfortably snug on my oval-ish head, but the cheek pads barely touched my face, which is super weird since I have a pretty full face (read: chipmunk cheeks). To confirm I had the right size I tried on a medium, which is just too tight on the crown and I couldn’t get it on all the way. While having a lot of room in the face is comfortable and makes your ride much cooler, it makes me concerned about the helmet staying in place in the event of a crash, which I didn’t have while wearing the Zox.