Thank you for your question on the Classic Kitchen Air Gap. I will be more than happy to assist you. The hole measurements are as followed: 1 1/4" (32 mm) minimum to 1 5/8" (41 mm) maximum mounting hole required. I have also attached the link to the specification sheet below for you to view. If you need anything further please contact us by calling 800-345-3358.
Delta Faucet Company
Date published: 2017-09-16