The Sieve Combo Set consists of four separate nesting sieves: a 120-micron sieve (Artemia); a 300-micron sieve; a 560-micron sieve, and; a 900-micron sieve. Each sieve is a well-constructed mesh-bottomed plastic receptacle (3.4" x 3.1" x 1.75" deep) which can be used to collect newly hatched artemia, copepods, eggs, larvae and other organisms. An indispensable item for every fish room. Let us know new ways you've found to use yours!