SpiderWire Ultracast Ultimate Mono
Diameter chart, reel capacity & backing guide
This guide covers SpiderWire Ultracast Ultimate Mono's 2018 US published Clear specifications only. It is the copolymer mono family, not Ultracast Braid or Fluoro-Braid. The chart retains that edition's 15 lb size and does not infer current stock, unchanged formulation or later package continuity.
- Construction
- Copolymer monofilament
- Listed strengths
- 4-20 lb
- Line type
- Monofilament main line
A mono plan with an edition-specific diameter
Ultimate Mono is a monofilament main-line option for anglers who prefer one continuous line to the lure. For a spool matching the historical range in this guide, compare its printed diameter with the reel's capacity. Choose strength for the lure and cover, and decide whether you need a full fresh fill or a shorter working section over sound backing.
How much Ultimate Mono will fit?
Calculated estimates, not measured fills. Stop at the reel manufacturer's fill level even if some line remains.
SpiderWire Ultracast Ultimate Mono diameter chart
2018 US Ultimate Mono Clear filler specifications ONLY. The 12 lb diameter is printed as .012 in in this edition. The 2020 edition prints .12 in and uses 14 lb where 2018 uses 15 lb; no 2020 numbers are imported or silently corrected here.
| Strength | Inches | mm | Spools (yd) |
|---|---|---|---|
| 0.006 | 0.1524 | 330 | |
| 0.008 | 0.2032 | 330 | |
| 0.009 | 0.2286 | 330 | |
| 0.011 | 0.2794 | 300 | |
| 0.012 | 0.3048 | 300 | |
| 0.014 | 0.3556 | 300 | |
| 0.015 | 0.381 | 300 | |
| 0.016 | 0.4064 | 270 |
Choosing your Ultimate Mono strength
The 4-8 lb rows are the light end of the 2018 table. Choose them only where the tackle and conditions suit their test ratings; extra spool capacity is not a substitute for adequate strength.
The 10,12,15 and 17 lb entries use the same published filler length in this edition, but their different diameters still produce different reel capacities.
The 20 lb entry is both thicker and supplied in a shorter filler package. Plan its working reserve independently rather than assuming one package fills every reel.
Keep the later 14 lb entry out of this chart. A changed strength label and a later diameter typo cannot be resolved by joining rows from different editions.
No independent stretch, strength, abrasion or casting test was performed. Manufacturer performance positioning is not treated as a measured ReelCalc result.
Want a guided recommendation?
Continue in the Setup WizardSame pound test, different diameters
At your selected strength
Loading diameter comparisons...
What changes with another line?
Nearby diameters in the line database
| Line | Strength | Inches | Difference |
|---|---|---|---|
| Loading line database... | |||
Backing, working line & leaders
Identify Ultimate Mono first
SpiderWire reused the Ultracast family name across different line constructions. Match Ultimate Mono on the package. Neither the neighboring Fluoro-Braid page art nor an Ultracast x8 braid label supplies this mono's capacity input.
Choose the edition's filler length
The 2018 Clear filler chart uses 330 yards at 4-8 lb, 300 yards at 10-17 lb and 270 yards at 20 lb. These are the 2018 test steps, including 15 rather than 14 lb.
Start with a full mono fill
A separate anti-slip backing layer is not required for the reason it may be used beneath braid. If you choose a shorter fresh mono section over backing, leave sufficient reserve above the connection.
Confirm the final level
Wind with even tension and stop at the reel manufacturer's recommended clearance. Check a newer package's own label before substituting its line into this historical calculation.
How Much Fits on These Reels?
Estimated full-spool capacity for the Ultimate Mono strength selected above, with no backing. These are calculated examples, not physical tests or recommendations for every pairing.
Loading capacity estimates...
Ultimate Mono questions, answered
Why is this guide specifically for 2018?
That official edition gives a coherent Clear diameter and package table. A later edition changes one test step and contains a conflicting 12 lb diameter, so the editions are deliberately kept separate.
Was the later .12-inch value corrected to .012 here?
No. The .012-inch figure is independently printed in the 2018 source used for this chart. The 2020 discrepancy is documented rather than silently repaired.
Are Ultimate Mono and Fluoro-Braid the same product?
No. They appear on the same historical catalog page but have different names and constructions. Only the Ultimate Mono section supplies this chart and image.
Why does the chart use 15 lb instead of 14 lb?
Fifteen pounds is the strength printed in the 2018 Ultimate Mono table. The later 14 lb entry is not merged into this edition-specific reference.
Does this establish current stock or formulation?
No. The page is a reference to 2018 US published specifications. A newer package requires its own label and formulation verification.
Specifications & sources
Checked September 13, 2026 against the original 2018 manufacturer catalog preserved by WesternBass. Inch diameters and the strength-specific Clear filler lengths were visually inspected; mm are explicit conversions. Original Ultimate Mono package artwork was retrieved from that same edition's asset manifest, distinct from its Fluoro-Braid artwork. No present-day availability or equivalence to a later formulation is claimed.
Calculations use the catalog's listed inch diameters. Published inch and millimeter values may differ slightly because of rounding.
- 2018 manufacturer Ultimate Mono chart Sole numeric source for this Clear filler chart; visually checked independently from the neighboring Fluoro-Braid table.
- Original 2018 Ultimate Mono artwork Unmodified manufacturer package-image asset from the same edition.
- Later catalog conflict, not chart input Catalog titled 2020 in this archive: documents the differing 14 lb row and printed .12-inch 12 lb value. Neither is imported into this page.