There are 2 different types of suction cups for VertiMax equipment; Metric and Imperial. 

How to tell which one you would need: 

*Imperial- Serial number is 5 digits and contains only numbers.  

Example: 81467

*Metric- Serial number is 10 digits long and contains both letters and numbers. 

Example: V80012E023

If you are unsure, please email us at:  support@vertimax.com