[Lars K. P.]

Hi´

Which axle standard from Rotor to be used for 2019 Cannondale Scalpel SE. Two versions available; standard and boost!

https://rotorbike.com/catalog/default/rotor/xc-mtb-marathon/cranks/kapic.html

Moreover, which spacers to apply for each side of the bottom bracket?

Thanks

 

[peabody]

You need boost for a boost bike, pretty self explanatory.
Spacers is dependent on which BB you decide to use.