Plastic Elevate Up 4 Inch: The external size: 4.25 * 4.25 * 3.3 inch. The internal size: 3.25* 3.25* 0.5 inch Heavy Duty: The New couch risers 4 inch heavy duty are made of high-quality plastic, the thickness of the plastic sheet is more than 1/8 ". A complex support structure is designed inside the risers which brings the bearing capacity twice Stackable: Bed lifters give perfect elevation with stack option. Except stack by themselves, you may also stack with our other variations ( 2 inch and 3 inch ). The bed frame risers lift 2 inch, 3 inch, 4 inch, 5 inch, 6 inch, 7 inch and 8 inch easily Occasion: furniture risers 4 inch fit to rise up desk, chair, sofa, couch, table, cabinet and dorm bed. Great for getting more under bed storage Package: 4 pack bed raising blocks from BTSD-home. Each bed leg extenders with one foam pad and one rubber bottom pad.(Tips: If stack, just stick foam pads at the elevator touching with furniture legs. Don"t stick each one.) bed raisers