Patent ID: 7650724

Claim:
A tube comprising: an inner hollow core bounded by an inner wall that consists of a first portion that is defined by a first curve based on a first circle having a first diameter, a second portion that is defined by a second curve based on a second circle having a second diameter that is greater than said first diameter, and a third portion that includes a pair of third curves, each third curve based on a third circle having a third diameter that is smaller than said first diameter and said second diameter, a first one of said third curves serving to smoothly transition between a first end of said first portion and a first end of said second portion and a second one of said third curves serving to smoothly transition between a second end of said first portion and a second end of said second portion, an outer wall with an overall circular circumference; and an external channel formed in said outer wall, said external channel extending parallel to a longitudinal axis of said inner hollow core, said external channel being bounded by a first channel curve formed by a first channel arm, said first channel curve being defined by a first radius, and a second channel curve formed by a second channel arm, said second channel curve being defined by a second radius, wherein said second radius is different from said first radius and a curvature of said first channel arm is different from a curvature of said second channel arm.