Square-shaped metal frames like the RB8157 rely on a 145mm temple arm to keep the fit even on both sides. That length is specific to this model, and a compatible arm needs to match it along with the metal finish of the front. Buying a shorter or longer arm to save a step on measuring tends to leave the glasses sitting crooked rather than level.

On boxier metal frames like this one, a bent or misaligned temple is usually what sends people looking for a replacement, while the square front is still perfectly straight. Swapping just the arm restores the fit without disturbing a front that never needed fixing. It's a quicker and cheaper aftermarket fix than sourcing an entire new pair of sunglasses over a single damaged part. A quick check of the model number against the arm's fit is usually enough to confirm it's the right one before ordering.

Frequently asked questions

My hinge feels loose — will new arms fix that, or is it the frame that's worn?

A new 145mm arm includes its own hinge barrel, so if the wobble is coming from worn threading on the arm side of the 8157, replacing it usually restores a snug, tight fold.

Can I replace just one arm, or do I have to buy both?

You can order a single side if only one arm on your 8157 is broken or scratched, or buy the pair if both need replacing — either way they match the 145mm length exactly.

What material are the arms made from, and will the color match my frame?

The arms are molded in an acetate or metal finish that matches the Square style of the 8157 closely, though very slight shade variation is possible since they're independently produced as separate aftermarket parts rather than cut from the same batch as the frame.

What if the arms arrive and the hinge doesn't line up with my frame?

Because each pair is listed against a specific model, in this case the 8157, mismatches are rare, but you're covered by a 14-day return window if the 145mm arms don't align with your hinge.