Adjustable Bed Riser System Instantly creates 3", 5" or 8" additional storage height under the bed Contains 4 of each small and large Customize to your own needs The bed leg or caster fits safely and securely into the recess cup built into the bed riser The small bed riser rests securely over the locking ring on the Large Bed Riser and will not slide. Made of High Impact Plastic Made In The USA Extra 3" high - use the Small Bed Riser Extra 5" high - use the Large Bed Riser Extra 8" high - use the Large and Small Bed Riser