There is not much to say about OSSA's wheels. They are pretty standard 18 x 2.15 and 21 x 1.60 trials wheels - which is great because replacements are readily available.

The early rims were manufactured by Fa-Ba in Italy, but I do not see anything like them in their current catalog. My 2015 bike has Morad (but unmarked) style rims. I really like the Fa-Ba methodology for tubeless tires in which each spoke nipple has an O-ring seal.

What is the purpose of a rim band in a tubeless tire? Is it to protect the nonexistent tube from the nipples? You tell me. Even a fancy, heavy, rim band is not a perfect seal. If your rear wheel has more than a very slow leak, replace the O-ring on the valve stem. My O-ring looked to be about 5/16" ID and about 0.077" cross-section. Maybe it is metric at 8mm ID with a 2mm cross-section? I did not have anything exact on hand so used something close with a dab of silicone sealer.

I use no rim band whatsoever in the rear.

Fa-Ba O-ring sealed nipple assembly

Valve stem and its O-ring

Wheel Bearings

Wheel bearings are a maintenance item. Replacements are commonly available. To the best of my recollection, they all have a rubber seal on both sides.

Rear wheel, disk side bearing 6004 (20 x 42 x 12mm)

Rear wheel, sprocket side bearings (2 required) 6905 (25 x 42 x 9mm)

Front wheel bearings, 6905 (25 x 42 x 9mm) same as rear sprocket side

Rear Tubeless Tire Mounting

Here is a tip. Prior to mounting the rear, inflate an 18" tube inside the tire to stretch and expand its sidewall. This is best done at least a day beforehand, preferably out in the sun.