Can I add casters & how much are they?
Sorry casters cannot be added to this unit but we do carry some shelfs that are compatible with our casters.https://honeycando.com/products/6-tier-black-18x48x72-600lbhttps://honeycando.com/products/5-tier-adjustable-shelving-unit-with-200-lb-shelf-capacity-blackhttps://honeycando.com/products/4-tier-black-14x36x54-250lb
Is it possible to order extra shelves?
No you can not add extra shelf to this unit.
36" L x 14" W x 54" H.