The Pisces Floating Pond Protection Kit is an interlocking floating solution for preventing predators such as Cats and Herons from getting to your fish, without making your pond look unattractive. The Pisces Floating Pond Protection Kit is designed to guard the perimeter of any pond whilst leaving the centre open. This helps protect the outside of the pond where predators are most likely to be striking from. Along with being easy to setup and place in the pond , they are also easy to clean and maintain. Individual pieces can also be cut with secateurs or scissors for customisation such as to make room for plants to grow through. The Pisces Floating Pond Protection Kit is a highly effective pond guard that simply clips together, and will fit any size or shaped pond. How to calculate the number of pieces required: Measure the circumference of the pond, divided the circumference by the diameter of one piece (27cm), this will give you the required number of pairs needed to protect your pond. Predators such as herons and cats will normally only strike at the edge of the pond and therefore it is not necessary to cover the whole pond. This 20 piece pack will cover approx. circumference of 2.7m (8.9ft²) OR surface area of 1.6m² (17.4 ft²). Measurements: Each Defender Disc: 27cm (10.5 Inches) x 31.5cm (12 inches) Each Pack Contains 20 Pond Defender Discs.