Adapter: 18mm female by 22mm male
Adapter: 18mm female by 22mm maleAdapter: 18mm female by 22mm maleAdapter: 18mm female by 22mm male

Free to AquaPurr customers for initial installation

Adapter is 18mm female on one end and 22 mm male on the other

 

This is a rarely used size. If you used one of the colorful plastic keys to remove your aerator then use the instructions to determine which metric sized adapter you need.