Cell size is 4.9mm. Suggested for use by experienced beekeepers only. Varroa Mite have a hard time reproducing on worker brood raised in small cell comb. Those beekeepers who on their own have tried this technique report good results, with varroa screens and drone foundation. Switching a colony of honey bees to small cell comb can be hard if not done at the correct time of the year. Honey bees first start major brood rearing in the Spring or right after swarming the beekeeper should introduce 10 frames of small cell foundation per brood chamber. So, if you are an experienced beekeeper who likes to experiment and want to move ahead of the chemical control crowd with your honey bee management, this may be for you. Size 8 1/2 x 16 3/4 inches