Eyewear Finder

Someone else's prescription won't work for you, so plan on new lenses. Pairs like this carry an orange label: RX lenses, Bifocal lenses, Progressive lenses, Reading lenses, Demo lenses or No lenses. Budget about $50 on top of the winning bid.

• Sun lenses, no prescription: Fuse Lenses cuts new lenses to fit your frame.
• Your own prescription: 39DollarGlasses puts prescription lenses in your frame. Get $10 off with Brett's invite.

Find your brand and model on their site, pick a lens, and pop the new lenses in yourself. Polarized and mirrored options are available, and lenses start at $29.99. If your model isn't listed, their custom service sends you a prepaid box: mail the frame in and they cut and install the lenses for $30 more, back within about three weeks. They can also make prescription sun lenses.

Their Lens Replacement service puts new lenses, prescription or not, into a frame you already own. Order online first, then mail the frame in using the instructions they send. Pricing starts at $48 for full-rim and half-rim frames, $58 for wrap styles and $78 for rimless. They inspect the frame when it arrives; if it can't take new lenses, they send it back and refund the lenses.

They show who in our group is bidding, so we don't bid against each other. Green means Brett is the high bidder right now; red means he's been outbid. Friends get their own color: a solid label means they're the high bidder, a dot means they've bid. A red "Brett & Sam both bidding" label means two of us are on the same pair, so talk before the auction ends. Friends are matched by the first and last letter of their ShopGoodwill username, so treat their labels as a heads-up rather than proof. Want your own label? Join Frame Spotter.

Join to get your own bid label, so the rest of us know not to bid against you. Brett approves each friend himself, and your label shows up at the next check after he does (8 AM or 5 PM CT).

Brett can also invite you to 39DollarGlasses. They'll email you a personal code for $10 off your first order. It works if you're a new 39DollarGlasses customer and you order with the same email you enter here.

Three measurements in millimeters, usually printed inside the left temple:

• Lens width (54): across one lens at its widest point. Also called eye size, and the one the size filter uses.
• Bridge (18): the gap between the lenses, where the frame sits on your nose.
• Temple (140): the arm, from the hinge to the tip, around the bend.

The box in 54□18 means the lenses were measured the standard optical way; a dash, a space or brackets mean the same thing. ShopGoodwill shows the box as a question mark, like 54?18.

1. Start with a pair that fits. Read the numbers inside its temple, or on the bridge of some older frames. That's your size.
2. No numbers? Measure that pair with a millimeter ruler: one lens across its widest point, the gap between the lenses, and the arm from hinge to tip.
3. Allow a little range. A lens within 2 mm and a bridge within 1 to 2 mm usually fit the same. Temple length matters least: within 5 mm is fine, and an optician can bend the tips. Metal frames with adjustable nose pads are the most forgiving at the bridge.

Small to XL. The size filter goes by lens width: small is up to 50 mm, medium 51 to 54, large 55 to 58, and XL 59 and up. Sunglasses usually run a few millimeters bigger than eyeglasses on the same face. Only listings that state a size show up when you filter, a little under half of them, so check “Size not listed” too. Open the size filter

Sizes in inches. ShopGoodwill often gives the width of the whole front in inches. Multiply by 25.4 (5.5 inches is about 140 mm) and compare it with your own pair, measured hinge to hinge. Vintage American frames from Bausch & Lomb, American Optical, Shuron and Art-Craft often mark the temple in inches: 5¼ is about 133 mm, 5½ about 140 and 5¾ about 146.

Bifocals and progressives. Pick a lens at least 28 mm tall (lens height in the diagram) so the reading area fits.

From the listing title and description, or the stamp inside the temple. Anything that mentions China is skipped. For houses that also make pairs in China, only vintage pairs, or pairs whose listing states a non-China origin, show up. Pairs made in Hong Kong count only when they're clearly vintage, since Hong Kong stamps were used on mainland-made frames for years. Valuations are estimates, not appraisals.