Searching for "I need something flat to put on the bottom of old wooden soda crates so they roll out from under our sofa" led me to these ball bearing casters (my name for them is MUCH shorter and equals mine I think it makes more sense) They were easy to install and rolled well on hard floors and thinner carpets Tip: Turns out these ball bearing casters come in a variety of sizes and capacities Think ahead to determine which size and capacity works best for your project . NOTE: These ball bearing casters DO NOT come with the hardware required to mount them to your project. This really makes sense given the many materials these devices can be attached to.