Markings such as 48□21-145 are useful reference values, but they do not describe the whole wearing width created by lens shape, DBL, rim thickness, endpieces and hinge position.
01 · EYE SIZE
The first number is the horizontal A dimension of the lens opening
In common spectacle sizing, the first number corresponds to the boxing-system A dimension: the maximum horizontal dimension of the box around one lens opening.
In 48□21-145, 48 usually refers to this A dimension.
Two frames with the same A dimension can still look and fit differently because lens shape, vertical depth and outline differ.
02 · BRIDGE SIZE
The second number does not describe the full three-dimensional bridge fit
In 48□21-145, 21 generally refers to DBL, distance between lenses, based on the boxing system.
It is useful for comparing frame geometry, but it does not tell you the actual internal bridge height, curvature, thickness or contact width on the nose.
This is especially important with plastic frames, where the same DBL can still produce a very different bridge fit.
03 · RIM THICKNESS
Rim and front thickness change external width
Even with the same A dimension, a thicker rim outside the lens opening can increase the external width of the front.
This difference can be especially noticeable in thick acetate frames.
04 · HINGE & ENDPIECE
Hinge and endpiece position also matter
The endpiece between the lens rim and hinge, together with hinge position, determines where the temple starts.
So two frames with the same lens numbers can feel very different in width if one has a longer endpiece or a more outward hinge position.
05 · TEMPLE LENGTH
The third number is not a complete statement of frame size either
A number such as 145 is generally the manufacturer’s nominal temple length.
Even with the same 145 marking, front width, hinge position, temple curvature and ear position can change the actual wearing result.
The printed size is a useful starting point, not the final answer.
SOLUTION GUIDE
Solutions at a glance
A reference for the lens opening’s A dimension.
DBL; it is not the full shape of the bridge on the nose.
Nominal temple length; real fit depends on the frame and wearer.
Compare rims, endpieces, hinges and total front width.
GLANOS FITTING CHECK
GLANOS fitting check order
- Front
Compare the printed size with the actual external width. - Nose pads / bridge
Judge real nose contact rather than DBL alone. - Width
Check endpieces, hinge position and temple direction. - Temple bend
See whether the nominal temple length suits the wearer’s ears.
CAUTION
Matching size numbers do not guarantee matching fit
Different brands and models can have different lens shapes, three-dimensional bridge structures, rim thicknesses, endpieces and hinge positions even with the same printed numbers.
GLANOS EYEWEAR
There is a reason glasses feel uncomfortable.
glasses size · lens size · DBL · bridge size · frame width · frame selection · eyewear fitting