RB8247 sunglasses use a round metal front on 145mm metal arms, slightly longer than the 140mm standard on most Ray-Ban lines. This aftermarket pair keeps that extended length and the round-curved profile, so it hinges into the front correctly rather than sitting a touch short the way a standard-length arm would. The prescription version, RX8247V, shares this same 145mm length and round shape, so the RB prefix is what confirms the sunglasses variant.

The extra 5mm on frames like the 8247 usually goes into the curve behind the ear rather than anywhere visible, which is easy to overlook when ordering — a 140mm arm can look almost right but sit noticeably looser. Checking the exact temple size before buying saves a return. If the old arm is available to measure, comparing it against a ruler is a quick way to confirm the 145mm figure before placing an order.