T-Slot WHITE bulb seal. the base is 3/8" round and not solid. is made by Amesbury Group. the bulb seal is round on the base. this is the bulb seal most window company use to seal the lower sash along the window seal. to help stop the air from coming in. The bulb seal can be easily replaced. if you look at the photo provided, it shows what it looks like and the sizes. if you have any questions. let me know I can help.