Three piece kit is harness compatible. Small dong is 5.5 in x 1.5 in for gentle exploration. Medium dong is 7 in x 1.75 in for powerful sensations. Large dong is 8.5 in x 2 in for deep and intense play. Suction bases provides a secure grip and easy control when attached to a smooth flat surface. Comfortable, durable SensaFirm is easy to clean and slippery when lubricated.