NL303  Teat cannula with adjustable nut 
 

• short, narrow, 1 inch diameter round-pointed metal tube used to pass from the exterior, through the teat canal and into the teat cistern.
• Used to relieve pressure in the gland when the teat canal is obstructed.
• Well-designed ones have a bulge followed by a constriction near the hub so that the tube is self-retaining.