There isn't a dress code I believe but I wouldn't recommend a skirt/dress since you are on a catwalk above workers at one point.
There is no specific dress code. Just like anywhere you must have shoes and shirt. There are no specific regulations to be followed. The guests are never in harm's way. There is a lot of walking so where what is comfortable for you.
Be also aware that you can't bring big bags. Especially when you get in the factory itself. There are also no cameras allowed but you can take pictures from the exhibition areas.
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