Sofa & Chair Requirement - Works best with Crevices 4 Inches or Deeper. NON Styrofoam - WeaselBlocks are Multi-Use SOFT FLEXIBLE Foam Inserts that will Not Damage Furniture & Upholstery to Include Leather. WeaselBlocks Firmly Secure your Sofa Slipcover in Place with No Movement, Slippage or Untucks Unique Rectangular Shape Resists Rolling, Slipping & Sliding Out to Firmly Prevent Slips & Untucks of your Sofa Slipcovers WeaselBlocks are NOT Styrofoam & Do Not Flatten Over Time with High Use & Work as Excellent Sofa Slipcover Tuck Grips Non-slip Slipcover Tuck Grips for your Sofa, Couch, Chair or Sectional US Veteran Owned & Veteran Employees to Ensure Complete Satisfaction