A small form factor is a computer form factor designed to minimize spatial volume, typically measured in liters. Generally, the phrase "small form factor" applies to desktop computers and not to computing systems that have traditionally been small, such as embedded or mobile systems. However, "small form factor" lacks a normative definition and is consequently misappropriated as a buzzword due to its growing popularity. Manufacturers often provide self-serving definitions. The size of SFF PCs vary widely, from 1 L to 30 L or more, but as of 2007[update] the volume of a shoe box is typical. Their shapes vary from cubes to mini-towers to shallow flat cases resembling home theater components (such as VCRs or AV receivers).