This thing was asked about in Question 6.3 from the second paper of 2009.

Features of the flanged tracheostomy tube:

  • The tube has a curved portion and a straight portion, which allows the flange to be adjusted to the appropriate pretracheal tissue thickness.
  • Adjustable flange allows adjustment of tracheostomy length to any length of patient neck
  • It is suitable for patients with up to 50mm of pretracheal tissue
  • Soft tube allows a degree of flexibility, especially when warmed to body temperature.
  • The tubing is reinforced, which prevents kinking
  • The material is MRI-friendly
  • High volume, low pressure cuff
  • Radio-opaque tubing allows visualisation of position on CXR (but there is no "blue line" like with ETTs
  • Some of these are designed for percutaneous insertion

References

A detailed autopsy of these devices can be found in the 5th edition of "Understanding Anaesthesia Equipment" By Dorsch and Dorsch. Section III, chapter 20.
This chapter seems to be available for free.