The full-length FOOTDISC insoles have a thickness of 0.4–0.6 cm (thicker at the heel). Please confirm that you have selected the proper insole size first. If there is no issue, it is necessary to remove the old insole from the shoe and replace it with the new one when using full-length insoles. Moreover, some shoes are designed using shoe lasts that are smaller than normal, so if you put in a new insole and cut it to fit the old insole and it still feels too tight, you might want to try a slightly larger size shoe. If you continue to experience difficulties, please contact our customer support at 0800-588-563.