These substantial, modular anti-fatigue mats keep workers productive, safe, and comfortable all day, every day. Extremely versatile, these 3 feet x 3 feet mats interlock on all sides to cover entire floor areas, long assembly lines or stand alone as single workstation mats. They are 5/8 inches thick and s are available: open with large holes to allow fluids and debris to flow through freely. Also available with gritworks, for increased traction (CFR and Nitrile versions). Both designs are available in general purpose (GR) 100 percent natural rubber for use in dry areas and around water, CFR a mineral oil based cutting fluid resistant formulation popular in industrial areas and 100 percent nitrile (NBR) For exposure to animal fats, petroleum-based and caustic industrial fluids. For extra safety attach optional 3 x 39 inches. Yellow safety beveled edges. Test specifications and results are MVSS 302 Flammability - "A" rating. It has a flame spread of < 1.6 and is labeled self-extinguishing, ASTM F1677 Coefficient of Friction - Dry: COF = 1.10 and Wet COF = 1.10, ASTM C501 Abrasion Resistance - Wear Index, 1/g=70, Federal Standard 191 Modified Tabor Abrasion - 1 percent loss, ASTM D 575 Compression Deflection - Deflection at 35 psi, mm= 8.02, inches = .315, ASTM D-1171 Ozone Resistance - Excellent, ASTM D1056 Temperature Range - 10 to 110 degrees fahrenheit, ASTM D 2240 Durometer - 55 to 60. Cleaning recommendations: Use a high-pressure hose (not to exceed 1800 psi) and hot water (max 160 degrees fahrenheit) to rid the mats of oils. For best results use a mild soap or detergent like Ivory Liquid with a ph between 4.0 - 9.0, to clean the mats. Do not use steam, degreasers or caustic chemicals. Do not machine wash or mechanically scrub the mats.