Gel combs for standard mini gels in 1.5mm thick plates. These are intended as replacements for the green plastic ones sold by a popular provider of electrophersis equipment. The 7 well variation has extra deep wells that hold ~125 uL each (versus the ~75 uL in a standard 10 well version).  Best to print at 0.15mm layer height.  At the lab website (http://www.psblab.org/?p=378) is a write-up with pictures, and also a .zip file with the original Sketchup file and a customizable comb, so you can use the push/pull tool to make any size wells.