I just bought a pair of these--450 grams for a pair in size 45, 540 grams with cleats installed. More than 300 grams lighter than my Sidi Ergo 2s. Should be ideal for the South Florida heat and humidity. Sizing is a little odd--these make a nice snug fit on me in size 45 (no thick socks), compared to 46 in Sidis. Fit like slippers, and my heels are held firmly in place. Much more secure than the Garneau x-lite carbons, and much lighter too.