The team behind the Square Reader have a keen eye for detail, so it’s no surprise that a lot of thought went into the redesigned Square Reader.

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The friction felt when a user swipes their card is a good example of how the team kept an eye on the fine points of the device.

The redesign also gave Dorogusker and company a chance to tweak the feel of the swipe itself, which is a crucial detail that makes the product itself feel trustworthy despite its tininess. By tweaking the design of the spring to which the magnetic read head was attached, the team was able to fine-tune the friction customers feel when swiping their card. At one point in development, they found that the level of contact they needed to successfully transfer data from a card resulted in a swipe that felt too loose. And when the swipe felt too loose, it felt like it wasn’t working, and would thus require another swipe. So they increased the friction above what was actually needed–an adjustment that was overkill from a technical point of view but resulted in a swipe that felt perfect to the hand.

One of the greatest improvements in the new Square Reader is that it doesn’t require a battery to operate anymore. Simplifying the device, and removing an additional point of failure.

In terms of the design of the internals, though, the chip offered another fantastic advantage: an opportunity to ditch the Reader’s battery. The old version relied on a coin cell, which added around two millimeters to the overall thickness of the device. With their own chip, though, Square was able to be much more efficient in their use of power, to the point that they could draw all they needed from the smartphone via the audio jack. As a result, the new Reader dropped the battery and two millimeters along with it. “For the nerds on the team, that is crazy awesome,” Dorogusker says.