A graft includes a flow tubing having a tubing portion defining a flow lumen. The flow lumen of the tubing portion is substantially free of ribs or grooves. A center line of the flow lumen follows a substantially helical path with a helix angle less than or equal to 65. The amplitude of the helix is less than or equal to one half of the internal diameter of the tubing portion.

A novel monofilament trimmer line is provided for reducing noise, reducing air drag and increasing durability by having a non-round cross-sectional shape defined as a polygon with three to six sides wherein the vertices between adjacent sides have been replaced with generous circular arcs, the arcs of a parabola, or even other arc shapes so long as the arc is convex and contains no sharp edges and wherein each arc is tangent to the two adjacent sides with a smooth and continuous transition, and the sides of the polygon are either straight or slightly convex, but not concave.

A novel monofilament trimmer line is provided for reducing noise, reducing air drag and increasing durability by having a non-round cross-sectional shape defined as a polygon with three to six sides wherein the vertices between adjacent sides have been replaced with generous circular arcs, the arcs of a parabola, or even other arc shapes so long as the arc is convex and contains no sharp edges and wherein each arc is tangent to the two adjacent sides with a smooth and continuous transition, and the sides of the polygon are either straight or slightly convex, but not concave.