Current factory production fits a 100T chainwheel (the late Sheldon Brown might insist this is in fact a beltwheel
) and a 30T rear cog.
On the current versions with 16" (ISO305mm) tires, it's about 49 gear inches.
On the current versions with 18" (ISO355mm) tires, it's about 55 gear inches.
Stridas have been fitted with Schlumpf Speed Drives and Efneo three-speed cranks. There's a factory model, the Evo, with a Sturmey-Archer three-speed bottom bracket gearset.