True-to-Size Millimeter Sizing Comparison
The North Face Sierra Mid Lace WP vs The North Face ThermoBall™ Traction Mule V
Detailed size conversion chart, cavity measurements in millimeters, and crowd-sourced fit advice for choosing your perfect size.
Interactive Size Converter
Select what size you wear in the Sierra Mid Lace WP to see your calculated size in the ThermoBall™ Traction Mule V.
Complete Size Conversion Matrix
Direct millimeter-calibrated mapping comparing all available sizes between both shoes.
| Sierra Mid Lace WP (US) | Internal Cavity | ThermoBall™ Traction Mule V Equivalent | Match Accuracy | Fit Difference |
|---|---|---|---|---|
| US 3.5 | 232 mm | US 3.5 | 53% | +4.0 mm |
| US 4 | 235 mm | US 3.5 | 88% | +1.0 mm |
| US 4.5 | 239 mm | US 4 | 100% | 0.0 mm |
| US 5 | 242 mm | US 4.5 | 88% | +1.0 mm |
| US 5.5 | 245 mm | US 5 | 88% | +1.0 mm |
| US 6 | 249 mm | US 5.5 | 100% | 0.0 mm |
| US 6.5 | 252 mm | US 6 | 88% | +1.0 mm |
| US 7 | 259 mm | US 6.5 | 65% | -3.0 mm |
| US 7.5 | 262 mm | US 7 | 88% | +1.0 mm |
| US 8 | 265 mm | US 7.5 | 88% | +1.0 mm |
| US 8.5 | 269 mm | US 8 | 100% | 0.0 mm |
| US 9 | 272 mm | US 8.5 | 88% | +1.0 mm |
| US 9.5 | 275 mm | US 9 | 88% | +1.0 mm |
| US 10 | 279 mm | US 9.5 | 100% | 0.0 mm |
| US 10.5 | 282 mm | US 10 | 88% | +1.0 mm |
| US 11 | 285 mm | US 10.5 | 88% | +1.0 mm |
| US 11.5 | 289 mm | US 11 | 100% | 0.0 mm |
| US 12 | 292 mm | US 11.5 | 88% | +1.0 mm |
| US 12.5 | 295 mm | US 12 | 88% | +1.0 mm |
| US 13 | 299 mm | US 12.5 | 100% | 0.0 mm |
| US 14 | 305 mm | US 13 | 76% | -2.0 mm |
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Frequently Asked Questions
How does the Sierra Mid Lace WP size compare to the ThermoBall™ Traction Mule V?
The ThermoBall™ Traction Mule V provides about 4mm more internal length than the Sierra Mid Lace WP. We suggest ordering 1/2 size down in ThermoBall™ Traction Mule V. The Sierra Mid Lace WP has an internal fit offset of -8mm compared to -4mm for the ThermoBall™ Traction Mule V.
Do these shoes fit wide feet comfortably?
The Sierra Mid Lace WP has a snug/narrow width profile, while the ThermoBall™ Traction Mule V is standard medium.