Kailh BOX switches are IP56 rated to keep dust and moisture out. Created with a box around the cross stem instead of the cross stem just sticking up, they’re built to avoid corrosion and debris buildup. The box extends to the contact plate and leaf, providing extra protection. This version of the switches is heavier than before for those who prefer a little more effort in their keypresses.
*For more information, you can download the spec sheet here.