3" bottom seal is the standard size of this durable and weather resistant rubber bottom. However, there are multiple different sizes and types of bottom seal available upon purchase, including black or gray. This specific 3" bottom seal is black in color and requires two T channel bottom plate. This bottom seal has two ends that represent a T and it loops as displayed in the photo. The T channel is the most popular but different manufactures offer different types of channel plates.
Bottom seal is priced by ft. Change the quantity to get the right amount of length. If you have a 16' door it's recommended to get a 1' extra.