These are wide fan feet for a Lasko box fan. They may fit other models.
They've also got round inserts on the underside. They're for fitting pillars to hold the fan off the floor in the event of water ingress; I just haven't gotten around to making and testing the pillars yet.
They're for a variable speed filter fan build I made. Video/article/BOM is available here: https://pcburn.com/box-fan-filter-variable-speed-fan-build/