For those that care, I read for a size 9, the racer weighs 160g, and the trainer 220g. I got to try a HTM trainers in size 10.5 and they were incredibly light, so I dont know if I would even care about added weight shedding lol.
I will comment a bit on sizing. I have wide feet and usually size up on narrow shoes. I normally wear a 10 in most shoes so that's what I hunted for. I could only find the HTM trainers in a 10.5 and took a gamble knowing I could try to trade them and/or I knew someone that would appreciate them and take them off my hands if they didn't fit. When I got them I immediately notices that although it was sleek and narrow in parts of the trainer, it did have a slightly wider toe box. The uppers have NO padding. All you get is this fine thin flyknit upper so there is a lot of room to play. My foot slid around like crazy. I could have tightened up the laces, but I knew I probably still would've felt a gap like urban's pic. I knew I needed a 10. I'm sure I could fit a 9.5 too. The uppers are so thin and flexible, people that size down will be fine. But I'm not sure it's absolutely necessary. I think it comes down to personal preference on how snug people like their shoes to fit. I personally like a little breathing room.
Thanks for the info. I do like my shoes snug and I have found that shoes that are snug, almost too much, on the first day, stretch after the first week and then fit perfectly after they conform to my feet.