Gravo The suction cup's diameter is 4 cm.Test it , weight test to exceed 8 lbs. Can hold the curtain easily ,don't worry about the suction.TIPS:The suction cup you received may be bent due to packaging transportation. Pour boiling water into the bowl, soak the suction cup for 5-6 minutes, dry and use.The blackout curtains have a good shading effect for home.When you are traveling,can easy to carry it .colour:blackMaterial:Polyestersize:198*130cmPackage Contents:1 * Curtain20 * suction cups20 * ringsOnly the above package content, other products are not included.Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.