Extremely strong: Our special manufacturing process gives our suction cups with knurled nut an unrivalled strong and long-lasting hold on smooth surfaces such as hallways, windows and walls or outdoors or in the bathroom. Easy to install: no drilling, no screwing, just clean the surface, press and secure with a knurled nut. Product details: 25 large suction cups. The actual size of the suction cup is 40 mm. Each suction cup can hold up to 2 kg. Versatile: Our suction cups can be sucked onto all smooth surfaces such as windows and glass, ceramic tiles, plastic, Formica, etc.