ISO/TS 16840-12:2015 specifies apparatus, test methods, and disclosure requirements for characterization of wheelchair seat cushion immersion and envelopment properties using instrumented indenters to characterize the interface pressure of each indenter and the test cushion by measuring the cushioning effects of immersion and envelopment. This part of ISO 16840 can be considered to expand the characterization of products intended to manage tissue integrity (ISO 16840‑2) and provide a standardized indenter for other wheelchair seating tests. It does not provide information specific to cushion performance for a particular individual user. ISO/TS 16840-12:2015 includes a method that is specific to 220 mm and 255 mm indenters. Dimensions and loads are provided for the 380 mm indenter to allow for extension of the methods for bariatric applications.