The design of the Zeiss ZM/VM rail is a 45° prism with an inner niche for mounting elements. When mounting a rife scope to a rifle with a purposely made rail you can easily see the advantages over the more traditional mounting with rings. For starters its quicker and easier, with no additional tools required for the procedure. The only main disadvantage when compared to rings is the price, which is usually a bit higher than rings, and the availability. Not all manufacturers produce rifle scopes which are fitted with rails. When you are mounting your rifle scope with the Zeiss ZM / VM rail you can clearly see the advantages: it improves the stability of the riflescope, it is more robust and reliable, the riflescopes main tube is not under stress and thus its constructionally intact.
Mounting with a rail does not leave mounting marks on the main tube and it is easier to achieve the proper eye relief. When mounting with a rail you always get a perfect horizontal level as the reticle is aligned with the rail. Mounting with a scope rail solutions is always the preferred way over the mounting with rings and in the future most of the European premium rifle scopes producers will exclusively use this approach. We are waiting on the first scope that will be produced with mounting rail only (apart from Zeiss Diarange which contains laser and cannot be mounted with rings at all). Torque values for tightening the mounting elements in the scope rail should be between 4-5Nm.
The main mounting manufacturers that are producing elements for Zeiss ZM/VM rails are: EAW, Recknagel, MAK, Rusan, Henneberger, Blaser and INNOmount.