They work but don't feel as warm as just the grips alone did and take a LOT longer to get warm.
I got them and love them for what they are. I like a thick grip, it makes me feel like I got a hold of something.
Living in South Florida year round I get very little use of the heated grips. They do take a little longer to heat up than stock, and they may not heat up as much as stock grips, which btw I haven't notice, what I have noticed is that I do have to turn down the heat in rare 40 degree riding temps. They do feel cooler to me in the summer than stock grips do, even while sitting in the sun.
My glove size is "8" (large) but not extra large.
My only beef is the chrome wearing off on some spots due to sweat from my bare hands, I guess if I wore summer gloves this wouldn't be an issue but then I'd have the "Mickey Mouse hands" look to contend with.
If I need to replace these anytime in the future it will be with another set of these. These have been in use for over 2 yrs now. I have pushed and pulled my trike and as a 2 wheeler with these installed without a problem.
I can't stand the thin stock GL1800 grips. So these clam-shell ISO grips are a blessing for me.