6pc Power head Replacement Suction Cups 3cm - aquarium fish tank tools size: 30mm x 16mm Very good Suction, Can use for aquarium and any glass surface. Not like other suction cups(easily be split away off), this item will not split away off the aquarium and any other glass surface!!! To attach, moisten the suction cup &amp; firmly press it against the glass wall Made from durable plastic &amp; easily attaches to aquarium walls.