MAS Outdoors Lawn Aerator Sandals, Turf Aerating Shoes, 2" (50mm) Metal Spikes (+1 Extra Spike), 27 Metal WASHERS, 3 Super Tough Nylon Straps per Sandal, Heavy Duty Metal (Zinc Alloy), $$$$ CHEAPER then renting an aerating machine, hiring a professional gardener and easier then pushing a hand lawn aerator. Ideal to use when mowing the lawn and complete two jobs in one, save TIME and MONEY. EXTRA METAL SPIKE, NUT & WASHER supplied with every set, 27 in total. The 2 (50mm) metal spikes are recommended by lawn experts to reach below roots to allow water, oxygen, grass seeds and nutrients directly to the roots and Carbon Dioxide to pass for a greener and healthier grass and the perfect lawn. ONLY SANDAL ON AMAZON supplied with metal WASHERS, to help distribute the pressure of the nut evenly over the sandal base, so that the surface isn't damaged and to ensure that the nut is pressed against a smooth surface, reducing the chance that it'll gradually loosen because it's in contact with an uneven surface. SINGLE SOLID PLASTIC Sandal/Shoe base (5mm thick) with heel support. Designed for easy assembly for the metal spikes and the 3 straps with several options for the straps to be feed through to allow tight fit for any shoe size. Only sandal/shoe on Amazon that provides 26 metal washers to allow stronger grip for the nut to the base and also prolong the life of the base. UNIQUE DESIGN which includes 3 SUPER TOUGH Nylon straps per shoe and HEAVY DUTY Zinc Alloy metal buckle. The buckle is a single feed for easy assembly with quick release and will offer longer life span compared with the cheaper plastic buckles. Avoid 2 straps sandals as they do not offer a tight fit and add extra pressure to the ankle strap and also the 4 strap which is pointless especially for the small shoe sized feet.