Action rods are called by various names, such as push rods, boot push pins, through drilled pins, and others. These are the simple rods that transfer the action of certain keys from one side of the boot joint to the other. They are used with the Bb trill key, the F# rocker, and the G key. Instruments with single hole G# systems also use one.
The 3 inch length is longer than will be needed for any bassoon. The pin will need to be trimmed to length to fit the individual instrument's needs. For the Bb trill and the F# rocker a small amount of free play is essential. For the G key the pin sets the actual pad height. Normal pad heights for that key are between 5/32" and 3/16".