There are a lot of them to collect, which is likely bringing the overall price down
This brand new set features Single Strike Pokemon, Rapid Strike Pokemon, and the first-ever Fusion Strike Pokemon
These can be cataloged under the Double Rares rarity in the Pokemon TCG, but do not necessarily translate only to rare Pokemon Ex cards, as trainers can be found with the Special Illustration Rare art
As for the benefits of using the right Pokmon sleeve size, there are: Firstly, using the right size helps protect your items from dust, dirt, and moisture
You find them for the recent set like a bundle of Edge of Eternities at big box stores and at a nice price point
I tend to run quite a few cycling lands in my mono-color decks, so Tilling Treefolk will provide some nice value if it gets back one or two of them