After a lot of searching and comparison, I chose these twin extra long bases for my king size memory foam mattress because these could be synchronized to work together and I didn't think I could get a conventional king base up my stairs. I got them on sale at a great price and they came two days earlier than promised! The quality of construction and materials was good so assembly was relatively easy. However, the base was made in Vietnam and the translation of the owners manual could be MUCH improved.