You can likely get them as an option on many combines. Or you can chose from different styles available from a handful of short-line manufacturers who saw a need and developed a product to meet the need.
They are shoe-shaped devices intended to run under the ahead of the combine tire. Their sole purpose is to knock over and smash down stalk stubs so that when tires run over them, they're not getting the brunt of the force that tough stalk stubs can deliver.
Pete Illingworth, who was driving this combine, says the devices do indeed help protect the tires. This machine is on its fifth season, and the tires don't show the wear and tear you might expect if the head didn't have these attached to it, he notes.
The real advantage in saving tire life is spreading the cost of tires over more years. He notes that since tires are so expensive, especially the large tires, it's worth investing a relatively small amount for equipment to run in front of the tires and protect them as much as possible.
Different models and styles are available from different manufacturers. Most fit most modern corn heads, and considering what they do, most are reasonably prices.
Many people blame the increased wear on tires on combines and tractors pulling grain carts in stalk fields over the past couple of decades on the advance of Bt corn. Some say the Bt stalks themselves are tougher. However, a university study at a location outside of Indiana a few years ago insisted that Bt stalks weren't any tougher than any other stalks that didn't have the Bt trait.
What plants with Bt traits often do, however, is stay healthier longer. That may mean stalk stubs are tougher just because the stalk wasn't already beginning to break down before harvest. Plant breeders make another point. Some say the increased stalk stub strength could be due to the fact that breeders are developing corn plants with tougher stalks through natural selection and by selecting for that trait whether the hybrids have the Bt trait or not.