A chain brake to stop the saw in the event of a kickback.
If you attend a fitness center or gym on a regular basis, you've probably seen some leg curl machines that target your hamstrings, and maybe a kickback machine that targets your glutes.
A kickback is where the chain or bar gets pinched and the saw comes up towards you.
Limited kickback over headsets are priced county tort filings.
Two carbide blades are fitted to the body and they are designed to provide integral chip limitation to prevent kickback.