The trundle drawer rolls out easily on 4 casters. You can use it under any CD bed for convenient storage or as an extra bed. 2 dividers can be easily removed to accommodate a mattress. Maximum mattress size is 38″ wide x 8″ high x 73″ long (78″ long in the extra-long model). Premier, Trundle and HealthCare mattresses will fit. View mattress options.