6-lobe hexalobular made as GO and NOGO pairs. Each gauge is designed to be held by hand and inserted into the torx hole. If the NOGO gage fits, then the hole is too large and the part fails inspection. If the GO gage fits, then the hole is the right size and the part will pass inspection. If the hole was too small the GO gage would not have fit inside.
All gages come with handles featuring green caps on the GO gage side and red caps on the NOGO side. NAS1800 (ISO 10664)