
The first number in the product name is the male thread, i.e. the size of the lens thread, and the second number is the larger female thread, i.e. the size of the filter to be used, for example.
The Nisin Ti Step-Up adapter ring is made of titanium. This material fits the adapters better than aluminum, the filter can withstand tightening and will not cut into it like aluminum adapters can. This means you take better care of the lens threads and filters.
In other respects, this Nisin adapter is of better quality. The inner surface is treated to reduce reflections. The outer surface of the ring has teeth that make it easier to attach and detach the adapter.