Basement door extension panels increase the door length of BILCO basement doors. You can find extension panels for our Classic Series basement doors in 6", 12", 18", 24" and 30" lengths. We also offer extension panels for our Ultra Series basement doors in 6" and 12" lengths. Plus, you can combine basement door extension panels to create virtually any size. BILCO products are made to the highest standards. So you know when you need to extend the length of a BILCO basement door, your best option is a BILCO basement door extension panel.