Package:20pcs Latex Rubber Cap Red Latex Rubber Dropper Head Cap Material:rubber Bulb inner diameter is 9mm; Outer max. diameter is 14.5mm,35mm in length,1.5mm in thickness Made of premium material,durable,corrosion resistant and strong suction,can be used in most dropper and glass droppers. Can be used for teaching equipment and chemical laboratory glass equipment,for all kinds of graduated tube,droppers,pipet,transfer pipette,ect. Great for all kinds of graduated tube, droppers, pipet, transfer pipette and so on.