The page protectors that are compatible with this album are:
Pioneer 12 x 12
I was a tad disappointed at first, that this album was a Pioneer album because I equated Pioneer with low-value stores like CVS and Walgreens, and this was a fairly high price to pay for a Pioneer album; however, this is a gorgeous album and rather than trying to make my CTMH pages fit it, I think I will go ahead and purchase Pioneer refills when needed.
As you might expect, I bought this for wedding photos and it is perfect. The bow actually lies quite flat, which pleased me and a nice vinyl cover. It also has an expanding spine which is not typical for Pioneer albums. I am very pleased with the quality.
The album is 12x12 but the refill pages actually fit an insert that is 11.75" x 11.75". On the instructions with the album, it explains the size of the insert and states that if you want to use YOUR cardstock, please trim yours to 11.75" x 11.75".
So while I am sympathetic to anyone whose pages are 12x12 and want to use this album and trimming is a hardship, I can't help but ask why the instructions very clearly printed on the first page weren't examined first. It contains some very useful information!