The elastic gravel guard (in this case Simms) is an inexpensive investment in protecting your stocking foot waders. The guard fits tight over the top of the wading boot and keeps a lot of gravel and grit out of the boot to cut abrasion against the neoprene stocking feet. You adjust the tension. One end has a velcro strip which provides strong closure. I have used these for years and find them a great investment. Although they are not really necessary, I use them when fly fishing lakes as well. Some stocking foot waders have a built in gravel guard that does an adequate job of filtering out gravel.