A warranty is a guarantee against faulty materials or workmanship. You are guaranteed that your product will not develop a fault caused by faulty workmanship or faulty raw materials. A 100 day sleep trial allows you to sleep on your new mattress for 100 nights before making your mind up. Simply arrange a free return within that 100 days and you will also get your money back – so 100 days to test your purchase, after which you lose nothing in the event you don't like it.