Does not slip and does not interfere during the race. The problem is if you have a certain volume arm (40 cm round, it is however not huge), the elastic, even at maximum width, you already tighten well.
I bought it to attach the GPS and be sure it does not fall. The belt is fulfilling its role and it is almost impossible to bring down the GPS even if held upside down. The size of the belt is adjustable and adapts to the contraction of the biceps dur
