for those with sprinter type C's

Mine are a black plastic.

Mine are grey plastic

we have 2007 LTV on a sprinter chassis our doors are metal and have a seal around them, dust has not been a problem. it will depend on the maker of the unit how well they seal.

2016 Thor- Siesta Sprinter 24ST Doors are aluminum and compartments are Rotocast plastic. Seem to be very durable. Also compartments are sealed.

Each RV manufacture chooses their own storage bin materials. You will have to ask the owners of each make & model.

Phoenix USA uses custom formed fiberglass enclosures to maximize storage and strength. The doors are insulated and gasketed to seal. We do not get water or dust inside our primary outdoor storage compartment which is considered an interior compartment with outside access for the sake of heat to protect the fresh water tank inside from freezing. The rear compartment gets a minor amount of water and dust inside but it is extremely minor, contemplating if I should even mention it. That one is considered a cold compartment, not heated.

My lower ones are metal with sealed doors. I've never had water intrusion.

My 2015 Itasca Navion's are made of Aluminum and are sealed tight.

Err...rust NOT dust!