Shimano 12 speed road cassette / freehub compatibility

[NHAero]

Please un-confuse me..

Shimano lists two Ultegra 12 speed cassettes:
https://bike.shimano.com/products/co...-R8100-12.html
https://bike.shimano.com/products/co...-R8101-12.html

Both say they fit a HG L2 freehub. However, they also say "Shimano ULTEGRA R8150 drivetrains maximize efficiency thanks to larger cogs and retain compatibility with existing HYPERGLIDE FREEHUB bodies".

To confuse the matter further, i was looking at the ultralight ZTTO cassettes on Aliexpress. It looks to me that these fit the standard HG freehub.

If I am specifying a new set of wheels with DT240EXP hubs, what am I ordering for the freehub, and does it differ between the Ultegra and the ZTTO?

Thank you!

[lunardds]

I believe they all fit the same hub. The 8101 is just a tweaked/newer version of the 8100 where they tweaked the ramps for shifting.

[RacerJRP]

The 8101 is officially approved for E-Bike use is my understanding. For normal bikes they are identical in function.

The Ultegra 12 cassette will run on a normal HG freehub or the L2. The L2 is not backwards compatible with 11 speed stuff though. L2 freehub looks similar to microspline as opposed to normal HG style.