The first answer is the frame width. A properly fitting frame will have its temples leave the frame front (chassis) and go directly back, touching the head just before the ear. A frame that is too loose or wide will constantly slide down the nose.
The bridge curve and frame rim should match the curve of your nose. You could have maximum contact with a little gap between the frame nose and bridge.
Ensure the nose pads are sitting comfortably on the nose, not too far apart nor too close together.
Frame temples or legs should be long enough to sit comfortably over your ears. Glasses with printed data inside the legs always indicate this measurement.
There are three kinds of replacement nose pads: Screw-in, Push-in and Adhesive.
The most common type of nose pad is the screw-in. Although it takes patience to mount, it’s not complicated. All you need is your replacement pads, screws, and a screwdriver. It’s always best to have your original screws, but if you lose them, you can purchase repair kits. These kits contain several sizes of screws and a screwdriver specifically for your pads.
Glasses and sunglasses have anti-slip and push-in nose pads, made of high quality soft silicone. Both comfortable to wear and non-slip.
Adhesive nose pads are used for eyewear without nose pads. They’re perfect if you need additional comfort. To use, peel away the paper to reveal the sticky side, then apply it to the portion of the frame that touches your nose.