Professional Otto set comes in 32,48,64 and 128 Hz Weighted Otto Set for Spine Tissue Nerve Healing Prongs physically move in a bigger motion, thus when the stem end is placed on the body, you can physically feel the vibration more and also feel the vibration at a deeper level WEIGHTED tuning forks are excellent to use individually with the stem placed on the body or by toning above & around the body Comes with a Mallet and a Velvet Pouch