This document details suitable equipment, a test method, acceptance criteria and advisable limits to help to ensure that there is compatibility (by measuring the insertion force) between a transfusion set closure piercing device (referred to in this document by the abbreviation 'spike') and a blood bag outlet port. The test procedure in its entirety is complex and beyond the scope of each of the relevant transfusion set and blood bag standards. This document was therefore developed to support the implementation of the existing standards for blood bags and transfusion sets. The procedure described in this document can be used by manufacturers of blood bags to test the compatibility with transfusion set spikes available on the market or by manufacturers of the transfusion set spikes to test the compatibility with blood bags available on the market.