This is an optional Post tracking service. It adds on to the flat rate shipping fee. The shipping and tracking service will be provided by USPS or Deutsche Post.
The tracking code is a way to trace your sample kit, while it's on the way to your address. It does not guarantee priority (fast) delivery or any other extra services.

(Regarding multiple kit orders: The max. weight is 8 oz. within the US or 500 g to other countries.)