Do I need any special paperwork or do I need to go through the red l customs for a product prototype

I will be taking a product prototype (it is not sale-able) to a Chinese manufacturer to use as a reference for building manufacturing samples. Since it is not a sale-able prototype (it is a kids non-motorized kick scooter value about 60$USA) can I just take it as luggage on the way in or is there something I must declare?
Upon leaving China we may leave with a manufacturing sample in addition to our prototype - I assume one or both products needs to be declared to US Customs when we arrive? (value of both product is about 60$USA).
Is there also some type of declaration to leave China that needs to be made? (and if so what do I need to do?)