Life-like models of real fish which are not only attractive, but serve a very important function in protecting valuable pond fish. Predators will not come back to a place where they were not able to eat. One of the most difficult problems for Koi owners is protecting their fish from predators and large birds in the heron family are the worst. Many valuable Koi are lost each year to herons. Realistic detail includes an attached weight to allow for their placement at differing depths and fish appear to swim and move if there is a current in the water or wind blowing. Herons are great stalkers but noisy eaters, so when they attack the decoys (tethered to a heavy rock) they leave disgusted and your real Koi are alarmed and hard to catch. Herons give up on a fishing spot that yields " No Food Here" Herons rely on surprise and stealth to catch Koi. When alarmed, Koi are extremely difficult to catch. A strike on the decoys signals an attack and every fish in the pond will respond to the signal that they are in danger. Small are 7" L x 2 1/2" H Large are 10" L x 3" H. Add Koi Kastles to give your koi protection from predators but still remain visible for your viewing pleasure. NycKK01 or NycKK02 Protects koi from predators. Aluminum frame & fiberglass mesh. Also provides shade , can be left in pond year round.