Ideal Pet Products makes the world’s most popular pet door and is used in the popular Fast Fit panel pet door. The vinyl flaps do need replacing every 3-5 years.
Ideal has discontinued the older rectangular logo flaps. These were in production until somewhere around 2005. They usually have the flap dimension and say "Made in USA". If you have one of these older pet doors, you will have to replace the entire unit.
The newer doors have a round logo embossed in the upper part of the flap.