Purchased for 1 sq. inch with 1/8" wall thickness. So the fill of the hole is .75 x .75. The product description says it will fit .70 to .80. Plugged in and 2 sides of the plug have been completely removed and the plug flipped. Designation
Pros
Size: 1"*1" plastic plug fits square tubing with 1"*" OD and an approximate ID of 0.75-0.9".