https://www.apple.com/retail/business/jointventure/terms.htm...
> Equipment Loaner Service. If the issue with your Mac Computer requires us to keep it for more than twenty‑four (24) hours, you will be provided the option of borrowing a similar Apple product from our pool of loaner products ("Loaner") based on availability at your local Apple Retail Store. Apple is not obliged to provide a Loaner that is the same as, or of equivalent or better functionality or appearance to your Mac Computer; nor does Apple make any representation that a specific software program is or will be installed on your Loaner. Please see below for additional terms and conditions relating to this Equipment Loaner Service.