These sheaths are specially designed to dilate the tissue which surrounds pacemaker or defibrillator leads. With the intention of being used once only, they are sterilely contained in peel-open packaging. Each sheath contains two long cannulae which are moderately flexible. One of these fits inside the other while still being able to move freely. The sheath is used to break up any fibrous adhesions by placing the sheath set over the lead. Contertraction is also helped when the lead tip is removed from the endocardial scar mass by stabilizing the wall of the heart. The sheath sets are available in different lengths: regular 13"/15" (33 cm/38 cm) and extra long 16"/18" (41 cm/46 cm). The latter can be used for patients who have a large thoracic anatomy or lateral venous entry sites.