First, I am a fan and advocate of Birkenstocks which is why I feel extra frustrated with customer service because I do love the brand. For years now I buy every year new Birkenstocks and lately I wanted to try som in-house Zermatt Premium Sherling. VEry nice for in house, especially during cold winter months. I wear them after taking a shower in the evening but unfortunately the black color stains my feet intensely. The stains are not only intense in color but also extremely difficult to remove. I can't wear them in the evening because it would effect my white bedding linen. Instead of taking my problem and request to return the item seriously. I received an email saying that there is nothing wrong with the product and that the recomendation is to clean my feet first with olive oil and after with Soap. To be clear, after taking a shower in the evening - the perfect time to wear these in-house- Birkenstocks, I have to take another shower to clean them. The oil and soap recommendation doesn't work by the way. My feet still look un-clean and it looks embarrassing when I am with people. Birkenstock, no matter if my return request was beyond the time frame, there is something wrong with this product and it would be appropriate to address factory errors accordingly instead of trying to justify the 'health and quality' of the product and sending me complicated cleaning guidelines on how to wash my feet. A Birkenstock fan. PS: I can share images but when I try to upload them I can't submit this review