For those who have never used bone-conduction headphones, they're worn around the ears and deliver sound through your cheekbones. The technology delivers good treble and midrange performance but falls well short in the bass department, making them less than ideal for music.With the OpenRun Pro 2, Shokz has solved the bass deficiency issue by adding a second, more traditional speaker driver that's tasked with firing bass frequencies toward your open ears. Shokz employed that same micro-speaker technology (it calls it "air conduction") in its first non-bone-conduction headphones, the OpenFit ($140) and Open Fit Air ($120) true-wireless earbuds.Some bone-conduction purists argue that the OpenRun Pro 2 isn't a true bone-conduction headphone because the air-conduction driver delivers a higher percentage of the sound than Shokz leads on. That may be the case, but that's not necessarily a bad thing -- and there definitely is a bone-conduction driver in the headphones. The dual-driver design doesn't radically alter the overall design of the headphones. The 30-gram OpenRun Pro 2 are still around-the-neck wireless headphones, sharing a similar shape to the earlier OpenRun Pro headphones and weighing only 1 gram more. But it's easy to spot the micro speakers that have been combined with the bone-conduction drivers.