THESE SHELVING UNITS ARE BOTH INDESTRUCTIBLE AND VERSATILE. I USE THEM IN MY OUTDOOR KITTY ENCLOSURE. I NORMAILLY BUY MULTIPLE 4 SHELF UNITS AND CREATE MY OWN 2-5 SHELF UNITS, DEPENDING ON WHAT I NEED TO FIT WHERE. I ALWAYS BUY THE 4 SHELF UNIT AS IT IS CHEAPER. WHEN THEY GET DIRTY, I JUST SQUIRT THEM OFF WITH THE HOSE AND WIPE THEM DRY...THEY ARE AS GOOD AS NEW. THE KITTIES LOVE RUNNING AND JUMPING UP AND DOWN FROM ONE UNIT TO THE NEXT TO THE NEXT.