There are two type of pince-nez frames, the spring bridge and the hard bridge. Generally, it is easier to adjust the spring bridge type for fit. The spring can be bent in or out to increase or lessen the bridge width.
The hard bridge type is preset at the factory. Generally, such frames have very little adjustment. When ordering, you must know your bridge width to get a proper fit. Your optician can provide this information.
Factory set bridge width varies between 14 and 26 mm. Generally, 14 to 16 is considered very narrow. Sizes 18 to 22 are the most common. Sizes 24 and 26 are considered wide.
Frames without metal rims offer more opportunity for today's needs. The new lens can be cut wider. The area below the pupil can be dropped down to make room for bifocal or progressive lenses. Frames that originally held round lenses can be adapted easily to hold an oval lens and vice a versa.
Wire rimmed frames work best with a single prescription, either reading or distance.
Two sample frames are below. The one on the top is a spring bridge, the one on the bottom is a hard bridge.