What is that piece of rubber tube on the lower brake caliper pin Honda Toyota Lexus Acura

NO HARDWARE / BRAKE SEALS. Do I have solid rotors or vented rotors? The item for 2005 2012 nissan xterra front and rear red brake calipers & rotors & pads is in sale since Sunday, August 16, 2020. This includes issues such as dust, rim coloration, and the overall life expectancy of your brake related parts.