Here's what Omnium has to say:

The puuuurfect spinning wheels for the Omnium Nano 20" bike.

Extra wide low profile rounded rim for the bulky tire choice (38mm outside, 32mm inside).

• • • 6 bolt Disc Hub
    • Thru Axle 142x12mm rear
    • 100x15mm front
    • Axles not included with wheels, but with frame.
    • Sealed bearings
    • HG free hub body
    • 32 spoke
    • Black Rim
    • Black stainless steel spokes
    • Brass nipples
    • 406 front weight: 855g
    • 406 rear weight: TBC