The Riese & Müller Birdy Touring is factory equipped with a 10s 9-32t Sunrace cassette (that requires a specific Sunrace rear hub).

I upgraded my two Birdy with and XDR rear hub and a 9-32t 3T/e13 cassette on one and a e13 9-34 cassette on the other one (with a Shimano Ultegra RD-R8000GS rear derailleur).

Moulton use a proprietary rear hub and proprietary cassettes with a 10t smallest cog, both the hub and cassettes are derived from Campagnolo hub freewheel and cassettes.