The Tech Team Reinforced Bed Riser set is a replacement for the caster wheels that most bed frames rest on. The bed risers can be installed without needing tools and fit over standard bed frame legs. The risers may not fit all bed frames. To ensure a good fit, measure your bed frame legs and compare with the provided bed riser measurements. On smooth surfaces, like tile or hardwood, a non-slip material may be needed under the risers to prevent sliding. Each riser is made from heavy duty hard plastic and has a steel reinforcement ring. The set comes with 6 risers.