A: Novatec hubs use 2 types of ratchet rings. Threaded type or press-in type. On the picture below you can see them both, press in type on the right-hand side and threaded type on the left-hand side of the picture. Now you should check which type of ratchet ring you have and let Novatec EU staff know this information. When asking for new rings (or any other spare parts) I recommend always specifying the hub model name and number so that we know exactly how many teeth your ratchet ring has, then we can offer you the correct one.

There are the following available ratchet rings used in Novatec hubs:
24 teeth: used in old hubs
27 teeth: used in recent hubs
33 teeth: used in new hub D462SB and D162SB
42 teeth: used in Novatec MTB wheels (hub XD642SB,XDH42SB,D542SB,DH42SB)
60 teeth: used in high-end Factor hub (XD602SB)
A ratchet ring removal tools for the threaded type of ratchet ring looks like this

A ratchet ring removal tools for press-in type ratchet rings looks like this:

A ratchet ring installation tools for press-in type ratchet rings looks like this:

The number of teeth determine also the Angle of Engagement. For 27 teeth you can calculate the angle like this: 360 degrees divided by teeth count.
360 / 27 = 13.33 degrees
The similar analogy you’ll use for any other number of teeth on the ratchet ring (24T, 33T etc.).
The number of teeth indicates also the Point of Engagement parameter so for 33 teeth there are 33 POI (provided all pawls engage simultaneously).
If the cassette body has 6 pawls that engage the first 3 of them then another 3, so not all 6 at the same time, POI doubles and the angle of engagement goes to half. The math looks like this for 27teeth: 360 / 27 / 2 = 6.67 degrees