drilled at 23 it has an axial passage extending from the lower end toward the upper end it terminates about half way through the device the passage provides a fluid flow route into the tool this is particularly helpful in avoiding the build up of pressure from down hole flow as the tool is run into a well bore fluid can flow upwardly through the passage 23 and escapes through a lateral passage 24 the passage 24 is located at some point upstream of the lower end of the passage 23 this provides a pressure release route the mandrel 17 includes an enlarged tapered portion 25 at its lower end the tapered surface 25 flares outwardly at a slight angle perhaps as much as 12 u00b0 but not more than this preferably it is not necessary to taper at a more severe angle the lower end of the mandrel 17 is rounded at 26 to define a smooth easily manipulated surface which has no square corners to snag or hang on other equipment the upper body 14 is drilled with the axial tapped passage 16 and includes an appended upper skirt 30 the skirt 30 is spaced outwardly from the upper portion 20 of the mandrel this defines a tubular cavity in the tool the skirt 30 terminates at a shoulder 31 the.