An introducer sheath or catheter can be formed in two or more layers with an inner layer made of a higher durometer material and an outer layer made of a lower durometer material. The inner layer can have one or a combination of the following: one or more longitudinal slits, overlapping portions, monolithic...http://www.google.es/patents/US7766820?utm_source=gb-gplus-sharePatente US7766820 - Expandable sheath tubing
