This is the bulb seal that is attached to the inside of the slide flange.
http://www.trekwood.com/products/137...k-Wall-1000-Bx
This is the wiper seal that is attached to the perimeter of the opening and seals against the roof and sides of the slides.
http://www.trekwood.com/products/137...lip-On-1225-Bx
You order by the foot and they cut it to the length you order. I usually order a length so I end up with about a foot extra. In order to replace the bulb seals, you have to remove the plastic corner pieces and they just slide out and the new slides in.