These trays measure 10.5" x 20.75" and have 288 cells in each.  The cells measure .75" in diameter and 1" deep. They are arranged in 24 rows of 12 cells. These trays are consructed of rigid black plastic. They are excellent for seed starting of individual plants that you later plan to transplant into a larger flat or pot for further growth.  These trays will give several years of use - Just wash and sanitize thoroughly between crops.