A lot of thought should go into specifying an ultra-low temperature freezer and this post is designed to help you sort through the considerations that apply. 

These units are not inexpensive; their function is to protect contents of high value and sometimes for long periods of time.  Fortunately, there are a number of ultra-low temperature freezers on the market to ease the selection of a model that best suits your needs.

What is Meant by Ultra-Low Temperature?

Good question.

There are freezers, low-temperature freezers and ultra-low temperature freezers on the market.  Here are some examples that apply to scientific (not commercial or household) freezers.  Note that different manufacturers may define the temperature capabilities of their various models differently.