How thin is too thin? When it comes to watches, Russian brand Konstantin Chaykin is pushing the envelope with its ThinKing Prototype. At just 1.65mm thick, it’s the world’s thinnest watch, with a K.23-0 movement integrated directly into its 40mm, heat-treated high-hardness stainless steel case. The dial is informed by the brand’s face-like Wristmon designs, with two “eyes” formed by the hour and minute displays and a smile composed of the engraved brand name. It’s so thin, in fact, that the company had to create a new strap to help manage the pressure from being worn, with elastic inserts and titanium supports integrated into the alligator leather strap. The movement can be manually wound via a key or by a special wearable carrying case that attaches to the back and can also automatically wind the movement, making the watch 5.4mm thick.