Cheaper tools essentially squash the terminal into an oval shape. With the Pro-HST the terminal fists with less space between the crimp nest-walls of the crimp die. The jaws then come down and compress the terminals so it has a more 360 degree compression of the terminal rather than just a squish action. In testing the Pro-HST beats all my others in terms of pull out strength for heat shrink terminals, including comparisons against high end German tools that cost 4X as much.