The bending stiffness (flexibility in longitudinal direction) of catheter - and stent systems as well as of expanded stents is an important parameter for the clinical application, in particular regarding the passage of difficult to access, tight stenoses, and the placement of stents in vessel curvatures. However, this parameter is judge very subjectively by the user. The measuring method offered by the Testing Laboratory permits an objective comparison of different products. The specimen is fixed in a clamping device. With the help of a linear drive a deflection of the specimen is achieved, whereby the resulting force and the free bending length is measured. The bending stiffness EI of the balloon catheter and/or stent is determined by reverse calculation based on the theoretic relation between deflection and resulting force of a cantilever of length l with a concentrated load at its tip.