it is normal to be able to move your heel up abit IF you are forcing it up, but it shouldnt really move when you are just flexing your boots, basicly any pair of boot you buy unless they are race boots you will be able to move your heel abit, but as i said only when you are trying to lift it up. if they are the right boots for you but you want to secure you heel abit more, cut 2 horse shaped pieces out of some sticky back 1/2mm thick high density foam and place it in a sutible place around the ankle and into the aqilies (sp) area. this should prevent any heel lift.