As others have said, they're the same, that's just PBK being stupid.
Most likely, the twin pack is shipped from the vendor as a different SKU/UPC than the singles. Most likely 23mm x2 was done in house by PBK with two singles. The descriptions were written by two different people. When the markdowns happen, they're most likely affected differently because of the different SKUs and no one has caught it yet because it's a sweeping discount across several items.
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Strava
