Hi. I have this Carrier a/c in my attic: FV4ANF005 (it was here when we bought the house)

For 6 years now I've always just used the 'traditional' 1" pleated filter.

However, I was just googling replacement filters and came across this: https://www.appliancefactoryparts.co...277406/110483/

Should I be using it along with the pleated filter?

On a related note, I believe I need this size filter: 19 7/8" x 21 1/2" x 3/4" , and that's what I've always used, but I'd like to know for certain what is the exact correct size I should use.

Here's a snapshot of a sticker on my a/c:


https://i.imgur.com/ovVNHQb.jpg

and I found this in an online manual:

KFAFK0212MED
KFAFK0312LRG
KFAFK0412XXL

This one, KFAFK0312LRG, seems to match up with the size I've been using the past few years (though it relates to the other kind of filter mentioned above).

In summary, 2 questions;

1) should I be using the 'blue' filter along with the regular pleated filter, and
2) what is the exact size (or model # would be great) of pleated filter that I should use?

I usually user Merv 8 if that helps.

I was planning on order this: 19 7/8 x 21 1/2 x 1 MERV 8 Furnace Filters | Air Filters Delivered unless you guys tell me otherwise.

Thanks for any help/clarification!