The grinders look like twins, they shared the same weight of 600+g, the same exterior adjustment design where 60 clicks per round, the same hopper volume of 30~35g, the shape of the conical ball.
It is unable to recognize which is which without looking into it.
The quickest way to identify the grinder is to remove the receiver and caught a glimpse of the burr set. The burr set of the K4 grinder is Titanium-Coated Burr whereas the K6 grinder is Stainless Steel Burr.
The major and only different is the burr set design.
The burr set design could affect your decision of purchasing the grinder.
The K4 grinder is tailor-made for the espresso. Why is that?
The K6 grinder is the ultimate grinder of the combination for the functional features and the affordable price range among the industry. It is able to grind several methods.