Stomach Tube Speculum. Speculum is useful for passing stomach tube in the conscious patient. The speculum is held in check by the canine teeth going through the two large holes. A round hole through the centre allows a stomach tube to pass through. By holding jaws firmly closed any chance of biting the tube is eliminated. The hardened blue nylon resists chewing and can be cold sterilised for reuse. Available in three sizes. Feline smaller size works well on cats and smaller dogs, 6mm (18Fr) opening. Standard canine has a 9mm (27Fr) opening. Large Canine has a 12mm opening.