Don’t you hate it when you can’t remember if you locked the front door when you last left your home? It’s a dreadful feeling that you don’t have to experience again thanks to a cool little accessory called CheckKEY.

Developed by Japanese lock manufacturer company Miwa, the ChecKEY is a sleeve-like accessory that goes over the top part of your regular key and features a small window that indicates whether you locked your door or not. The ChecKEY comes with a built-in mechanism that detects when you turn the key clockwise or counterclockwise and changes color accordingly. When you turn the key into a lock clockwise, the little window on the ChecKEY turns white, and when you turn it counterclockwise, it turns orange. The mechanism is entirely mechanical, so it never runs out of batteries. This way, when in doubt, you can just look at your key and tell if you really locked your door on your way out.

“Approximately 40% of burglaries are caused by people forgetting to lock their doors and windows, and the number of people forgetting to lock their doors and windows is on the rise,” Kenichi Tanaka, manager of Miwa’s product planning department, told Japanese magazine Withnews about the inspiration for a product that people seemed to genuinely need.

The original ChecKEY hit the market in 2012, and since then, Miwa claims to have sold over 130,000 units nationwide, making it one of the company’s most successful products. Last year, the ChecKEY II, a sleeker version of the original, came out and managed to attract a lot of attention on social media. People were in awe of it, claiming that they had no idea such a gadget existed and that they needed it in their lives.

The ChecKEY II is compatible with most common key shapes; all you need is a screwdriver to attach it. The company clarified that the mechanism inside the gadget is only activated by turning the key into the lock, either clockwise or counterclockwise, so there is no risk of the window changing color in your pocket or by simply inserting the key into a lock.

Miwa points out that the ChecKEY system allows users to check their most recent key operation, which isn’t synonymous with locking the door the last time they left home. For example, if you lock your door and another family member comes home before you return, the window on the ChecKEY will display the locked state even if you forget to lock the door the next time you leave home. To prevent this from happening, the company recommends inserting the key into the lock and turning it even if it’s already unlocked, to reset the window on the ChecKEY. Obviously, if you live alone, this won’t be a problem.

 

The ChecKEY II is available on Amazon for $23.42 and on the Miwa store, for just 1,595 yen ($10.80). That’s a small price to pay for peace of mind!