Slippers buying request Germany

We are interested in some slippers in the form of a bulky plush animal, e.g. a current animal already existing on our clients merchandise shop. We would like to know what extent of personalization you can offer and which expenses we should expect. The rough estimation for our aimed production quantity would be a five-digit-number. As it is a product which normally depends on the consumer’s shoe size we would also like to know about your sizing chart and if you offer a one-.size-fits-all. Our aimed consumers are between the ages of 8-14.