IEC 61300-3-33:2012 describes the procedure to measure the withdrawal force between the ferrule (gauge pin) of the plug connector and the resilient alignment sleeve of the adapter. The gauge pin should have the same shape (chamfer) like the normal ferrules described in the optical interface, see IEC 61755-3 series and IEC 61754 series. This measurement procedure is applicable to single-fibre cylindrical ferrule optical connectors. The changes with respect to the previous edition are to reconsider the entire document according to the updated IEC rules and to add a gauge and a solvent into Clause 4, and to add a general subclause and cleaning procedure into Clause 6.