A process of making a multi-layered product from an extruded sheet or web of material (42) having parallel upper and lower walls (130) and a plurality of spacers (134) extending between the upper and lower walls (130) is provided. Portions of the extruded web or extrudate (42) are removed in selected areas. The lightened web is then folded. Outer skins are then applied to the folded web. The extrudate (42) is formed into a product (10) having a plurality of cells (14). The cells (14) may have one or more openings (34), allowing access to an interior of the cell (14) and reducing the weight of the product (10).

Embodiments of an expandable sheath can be used in conjunction with a catheter assembly to introduce a prosthetic device, such as a heart valve, into a patient. Such embodiments can minimize trauma to the vessel by allowing for temporary expansion of a portion of the introducer sheath to accommodate the delivery apparatus, followed by a return to the original diameter once the prosthetic device passes through. Some embodiments can include a sheath with inner and outer layers, where a folded portion of the inner layer extends through a slit in the outer layer and a portion of the outer layer overlaps the folded portion of the inner layer. Some embodiments include an elastic outer cover positioned outside the outer layer. Embodiments of the present expandable sheath can avoid the need for multiple insertions for the dilation of the vessel, thus offering advantages over prior art introducer sheaths.