actual says 7.5” & thickness is about .375” per answered questions, so is it a total outside dia. 7.5” or 8.25”

The inner diameter of the QUIKRETE® QUIK-TUBE® varies up to +/- ½ inch from the stated “common” diameter. They are not intended for use in projects requiring precise dimensions. They are sold in 4 foot lengths only, which may be cut to size if a shorter length is needed. QUIKRETE® QUIK-TUBE®’s are designed specifically as lightweight, single-use forms for a variety of cylindrical concrete applications, such as footings or setting posts. Additional support (wooden collar or frame and side braces) must be provided if the tube extends two feet or more above the ground line.