Air-Tite Capsules come in a variety of sizes but the CAPS system only has pages for A, T and H capsules
You have 2 types of Capsule - Direct Fit and Full size, although some full size capsules are direct fit for a specific coin such as an H or H-40 is a direct fit for an
ASEDirect fit refers to a reduced inner diameter to fit a specific coin that is smaller than the full size ID of the capsule
Example - An H-38 is a direct fit for a dollar size coin such as an Ike, Morgan, peace or Commemorative
If you want to use the black or white foam ring you buy the ring size in MMs that is equal to a direct fit for that coin
Example, if you want to use a black ring for a
Morgan dollar you use and H or H-40 capsule with a 38MM black foam ring
Air-tite has rings for every size coin that will fit into a specific capsule
You can fit just about every coin into a H sized capsule using rings but obviously cannot fit a
Peace dollar into anything other than an H sized capsule
The disadvantage of direct fit capsules is that sometimes the coins get stuck and unless the coin fits the full size version you cannot read the edger lettering
Example - I have 2016 ASEs in H capsules and you can read the edge lettering
The disadvantage of the rings is that you are normally using a larger capsule for a smaller coin so it will take more pages
Example - I use A pages for my quarters and can get 30 per page, if I used Direct Fit T capsules that would be reduced to 20 and if I went with Black Ring H Capsules it would only be 16
I hope this helps you understand the Air-Tite system a little better