All blades on this page are suitable for the Gardena Sileno City 500 robotic lawnmower. This lawn mower uses three blades. We therefore sell the blades in multiples of 3 and always supply enough screws. Because the robotic lawnmower mows every day, the blades wear out relatively quickly. We therefore recommend replacing the blades every two (with stainless steel blades) to three (with stainless steel titanium coated blades) months. We use volume discounts on our website. If you order more blades, they will be cheaper per piece. You can easily choose the number of blades you want on the product page. Shipping is always free with us, even with small quantities.