This includes 1 endcap that fits the premium kits.
It is 6065-T6 Anodized Aluminum, 18mm thick with a center hole 13/16" x 16 tpi (threads per inch). It is milled from a solid piece of aluminum.
TIP: some folks like to use one of these on their filter kit while outdoors and then switch back to the solid end cap when indoors or traveling.
These are thick enough to drill your own pin holes so you can use your pin wrench to open and close the tube (see video).