this is an implantable vaso - occlusive device . it is typically a vaso - occlusive coil comprised of a primary helically wound coil which may then be wound into a secondary shape . central to the invention is the use of a stretch - resisting member fixedly attached within at least a portion of the primary coil . the stretch - resisting member may be formed into coil tips at the ends of the coil by melting the polymeric fibers or alloys or by attaching the fibers with a glue . this stretch - resisting member is for the primary purpose of preventing stretching of the coil during movement of that coil , e . g ., by retrieval or repositioning after deployment . the device typically has a self - forming secondary shape made from a pre - formed primary linear helically wound coil , although it need not have the secondary form . external fibers may be attached to the device and affixed to the pre - formed linear member to increase . the vaso - occlusive member may be also be covered with a fibrous braid . the device is typically introduced into the body through a catheter . the device is passed axially through the catheter sheath and assumes its secondary form upon exiting the catheter .