We really don't like the metal tubes, in in-experienced hands they can do so much damage to birds and animals - often resulting in death. These flexible tubes are so much safer.
The small tube is suitable for such birds as budgies, cockatiels and larger softbills. This tube fits onto standard syringe nozzles.
The larger tube is recommended for parrots and fits the catheter tipped 60ml Feeding syringes.