Probably OK for a short commuting ride where you don't have to swap bar positions and can just ride on the hoods. Similar things are sold for m/cycles and work reasonably well. They are better than gloves because they protect all the fingers [individual little heat losing radiators] and form a "still" pool of air around them. Main fault I can see is in the rain. If your stood in traffic the rain is just running down inside and it appears you could end up with your hands in two little bags of cold water.