These are all Tech style razors. These pictures show how they differ in dimension. As far as gap, my crude measurement puts the EJ at .030 inches, HD at .030 inches, and tech at .025 inches. I'm using a tapered gap gauge, not designed for this. In the pictures it goes tech, HD, and EJ from top to bottom and left to right. By the way, the EJ is a three piece, like the tech. The HD is a two piece, and the easiest to load up with a blade.