In aviation, when an aircraft is made and delivered it will come with all agreed SFE equipment. The opposite of SFE is buyer-furnished equipment (BFE), which is purchased by the buyer and given to the aircraft manufacturer to be installed before delivery by the aircraft manufacturer. SFE is alternatively referred to as forward fit, while BFE is referred to as retrofit. Typically the SFE is elegantly integrated appearing as a natural part of the original system. BFE in contrast often appears to be a late 'bolt on' that interrupts the smooth lines and operations of the original system. BFE also includes preferred galley equipment (ovens for example). In many cases the aircraft is designed to accommodate the BFE during the initial engineering phase.
In contrast is buyer-installed equipment (BIE). BIE is when provision is made for specific equipment the buyer will buy and install, e.g. first-aid kits and life vests.