Written and maintained by CASRAI Editorial Board
Last updated
General product information from manufacturer documents, not medical advice. Which stent a patient receives, and in what size, is decided by their treating clinician.
A ureteral stent is a hollow tube that provides temporary internal drainage between the kidney (the ureteropelvic junction) and the bladder. Manufacturers describe its size with two numbers: a diameter in French (Fr) and a length in centimetres. The chart below lists the Fr and length combinations printed in one manufacturer’s own product tables, so you can read a specification, match a catalogue entry, or compare a listed set against what a department stocks.
Ureteral stent size chart (Cook Medical product tables)
Values are taken from the Cook Medical product pages listed under Sources (checked 2026-10-30). They show one manufacturer’s range, not every stent on the market.
| Cook product | Diameter (Fr) | Lengths (cm) | Stated material |
|---|---|---|---|
| C-Flex Double Pigtail Ureteral Stent Set | 3.7 | 8, 10, 12, 14, 16, 18, 20, 22 | Not stated on product page |
| C-Flex Multi-Length Ureteral Stent Set (with tether) | 3.7 | 8 to 20 (one stent covers the range) | Not stated on product page |
| C-Flex Multi-Length Ureteral Stent Set | 3.7 | 21 to 32 (one stent covers the range) | Not stated on product page |
| Black Silicone Filiform Double Pigtail Ureteral Stent Set | 6.0 | 20, 22, 24, 26, 28, 30 | Radiopaque black silicone |
| Black Silicone Filiform Double Pigtail Ureteral Stent Set | 7.0 | 22, 24, 26, 28 | Radiopaque black silicone |
| Black Silicone Filiform Double Pigtail Ureteral Stent Set | 8.5 | 22, 24, 26, 28 | Radiopaque black silicone |
Check your product’s labelling. Reference part numbers are not the same in all countries or regions, and a size offered by one manufacturer may not exist from another. The product label and instructions for use (IFU) are the authority for the item in your hand.
How to read the chart
What does “6.0 Fr, 24 cm” mean?
The first number is the diameter of the stent in French units and the second is its length in centimetres. In the Cook tables, each size has its own order number.
What is a double pigtail stent (ureteral stent diagram in words)?
“Double pigtail” is the manufacturer’s name for a stent that has a coil (pigtail) at each end, as the product name indicates. Cook’s black silicone model is supplied as a set with a tether and a stent positioner, according to its product page.
Fixed length versus multi-length
The fixed-length C-Flex set is listed in eight lengths from 8 to 22 cm. The multi-length sets are sold as two models, 8 to 20 cm and 21 to 32 cm, where each stent is described as covering its range instead of being one fixed length. The 3.7 Fr size is described by Cook as indicated for pediatric patients.
French size versus millimetres
The French scale is a diameter scale in which one French unit is about one third of a millimetre (diameter in mm is roughly Fr divided by 3). The French catheter scale table in the open-access chapter by Ford and Mazzaferro (PubMed Central PMC7158358) lists, for example, size 9 as 3 mm. Applying that factor gives about 1.2 mm for 3.7 Fr, 2.0 mm for 6.0 Fr, 2.3 mm for 7.0 Fr and 2.8 mm for 8.5 Fr. These are approximate conversions, not manufacturer-stated millimetre dimensions; the Cook pages give French sizes only.
Ureteral stent material
Only the materials a manufacturer states are listed here. Cook describes its filiform model as radiopaque black silicone and notes that it is not intended to remain indwelling more than twelve months. Boston Scientific describes its Contour stent as made of soft Percuflex material with a HydroPlus coating, offered in fixed and variable length versions, and lists further lines such as Tria (Percushield technology), Polaris Loop (dual-durometer, with two bladder loops) and Polaris Ultra (a Nautilus Bladder Coil). The Boston Scientific category page does not give French sizes or lengths, so no size values are shown for those lines.
Common mix-ups
- Fr is not millimetres. A 6.0 Fr stent is about 2 mm across, not 6 mm.
- Multi-length is not one length. A multi-length stent is listed by a range, so the range must be matched to the ordering model.
- A size on one brand’s chart is not a size on every brand’s chart. Part numbers differ by region as well.
- MR Conditional is a labelled condition, not a blanket approval. The Cook pages mark these stents MR Conditional; see what the MR Conditional label means and read the IFU for the conditions.
- Catheter sizes are not stent sizes. Urethral catheters use the same Fr scale but are different devices; compare, for example, the Robinson catheter and Malecot catheter guides.
FAQ
What sizes do ureteral stents come in?
In the Cook Medical tables on this page, diameters are 3.7, 6.0, 7.0 and 8.5 Fr, and lengths run from 8 to 32 cm depending on the model. Other manufacturers publish their own ranges.
Is there a single ureteral stent size chart for all brands?
No single chart covers every brand. Each manufacturer publishes its own sizes and reference numbers, so use the chart for the brand and model on the label.
Which size is right for a patient?
That is a clinical decision for the treating clinician, and the manufacturer pages cited here give no rule for it, and this page does not provide one.
How long can a stent stay in?
It depends on the model’s IFU. Cook states that its black silicone filiform stent is not intended to remain indwelling more than twelve months.
Related reading
For where stents sit in a wider stock list, see the urology clinic supply checklist. Related supplies are available in the gynecology and urology supplies category.
Sources
- Cook Medical, C-Flex Double Pigtail Ureteral Stent Set: https://www.cookmedical.com/products/uro_cflexpigped_webds (checked 2026-10-30)
- Cook Medical, Black Silicone Filiform Double Pigtail Ureteral Stent: https://www.cookmedical.com/products/uro_fdp133_webds (checked 2026-10-30)
- Cook Medical, C-Flex Multi-Length Ureteral Stent Set: https://www.cookmedical.com/products/a1a2a5e6-7fd5-44b5-8911-497da81a1d8c (checked 2026-10-30)
- Boston Scientific, Ureteral Stents: https://www.bostonscientific.com/en-US/products/stents–ureteral.html (checked 2026-10-30)
- Ford RB, Mazzaferro EM. Diagnostic and Therapeutic Procedures. In: Kirk and Bistner’s Handbook of Veterinary Procedures and Emergency Treatment. https://pmc.ncbi.nlm.nih.gov/articles/PMC7158358/ (checked 2026-10-30)
