A 1-inch inside-diameter rubber grommet has a nominal central passage of 25.4 mm. That measurement does not define the mounting-hole diameter.
Check the groove diameter, panel-thickness range, flange diameter and overall thickness on the drawing. The mounting cutout must suit those features. Also confirm cable or tube clearance and any connector that must pass through the opening.
A 1-inch internal passage is not a universal fit for equipment or walls. Select the compound for the actual environment and verify any sealing, retention or vibration requirements separately. Use the complete specification to confirm suitability.
