Thetford Service / Locker Door Seal ? SD3 .
Check the sticker inside door / frame for part number of door , this will give you SD number.
Thetford part no 26901.
Colour - Black
Genuine Thetford replacement rubber door seal designed specifically for the SFD3 / FD3 Flush Door fitted to caravans and motorhomes. The seal fits around the door and helps provide a weather-resistant closure, preventing water and dirt entering the locker or compartment.