DNS Zone hosting

We are investigating moving our dns zones for a few domains to a new hosted dns provider. Domains are not registered through OVH.

I noticed pricing is listed as included when ordering a new dns zone in the interface. I am wondering if hosted dns is indeed 'gratis' and am wondering if there are any restrictions or limitations, e.g.

- record limit;
- (monthly?) query limit;
- any limitations on amount of hosted zones;

Anything else which may be of note to this that I have not asked.