Immediate Teeth Bleaching Custom Traysstar rating 4WillFebruary 10, 2011The instructions for forming them are ok but the first time you do it, you may not get a great mould or you may do what i did accidentally and pierce through the tray on one or more teeth. Careful to avoid doing this, don't bite down too hard or press the trays too hard on your teeth. Other than that, great product