JBL and Under Armour bill their new True Wireless Flash ($170) as totally wireless sports earphones "designed for runners by runners." They're technically the first truly wireless earphones from the duo and as far as truly wireless sports earphones go, they're quite good, although some of their allure is tempered by a rather large charging case that's probably three times the size of Apple's AirPods' charging case.

The first thing you'll noticed about the earphones -- and the "rugged aluminum" charging case -- is they have some heft to them. By that I mean they feel solidly built, and in the case of the earphones, while they aren't heavy per se, they certainly weigh more and are bigger than the AirPods. The charging case is a little heavy, weighing in at 4.2 ounces (118 grams) with the earbuds inside.

These being sports earphones, they include three different-sized sports fins and tips (JBL calls them "Flex Ear Tips") to help lock the buds in your ears with a tight seal to maximize sound quality. I achieved a good fit with the medium fins and large tips and I found the buds fit comfortably and securely. I was able to run with them without a problem and they performed well with minimal Bluetooth hiccups in New York City, which is filled with wireless signals that can cause interference problems for lesser true wireless earphones.

The earphones are equipped with 5.8 millimeter drivers and are fully waterproof, with an IPX7 rating, which means you can submerge them in 3 feet/1meter of water for up to 30 minutes. (No, you can't swim and listen to music with them -- Bluetooth doesn't transmit through water.)

I thought they sounded decent -- on par with and even slightly better than other true wireless headphones in this price class. They sounded well-balanced, with fairly natural sounding mids and meaty bass that's pretty well defined (read: not boomy). You're dealing with Bluetooth streaming so you're not going to get as clean or detailed sound as you would with a good pair of wired headphones, but most people should be pleased with the sound quality.

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Like a lot of true wireless headphones, battery life is rated at 5 hours and you get four additional charges from the battery case.

As I said in the intro, these are designed with runners in mind. The UA True Wireless Flash features something marketed as "Bionic Hearing," a "unique sound and mic technology, enabling athletes to hear surroundings with two sound technologies: TalkThru and AmbientAware." It's similar to other "transparency" modes found on other headphones and earphones, so I'm not sure how unique it is, but it's useful enough.

With TalkThru Technology, your music is lowered and speech is amplified when you touch the button on the outside of the left bud. Tap it again and your music volume returns to the previous level.