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 | 234 mm | US 3.5 | 43% | +4.8 mm |
| US 4 | 237 mm | US 3.5 | 79% | +1.8 mm |
| US 4.5 | 241 mm | US 4 | 91% | +0.8 mm |
| US 5 | 244 mm | US 4.5 | 79% | +1.8 mm |
| US 5.5 | 247 mm | US 5 | 79% | +1.8 mm |
| US 6 | 251 mm | US 5.5 | 91% | +0.8 mm |
| US 6.5 | 254 mm | US 6 | 79% | +1.8 mm |
| US 7 | 261 mm | US 7 | 43% | +4.8 mm |
| US 7.5 | 264 mm | US 7 | 79% | +1.8 mm |
| US 8 | 267 mm | US 7.5 | 79% | +1.8 mm |
| US 8.5 | 271 mm | US 8 | 91% | +0.8 mm |
| US 9 | 274 mm | US 8.5 | 79% | +1.8 mm |
| US 9.5 | 277 mm | US 9 | 79% | +1.8 mm |
| US 10 | 281 mm | US 9.5 | 91% | +0.8 mm |
| US 10.5 | 284 mm | US 10 | 79% | +1.8 mm |
| US 11 | 287 mm | US 10.5 | 79% | +1.8 mm |
| US 11.5 | 291 mm | US 11 | 91% | +0.8 mm |
| US 12 | 294 mm | US 11.5 | 79% | +1.8 mm |
| US 12.5 | 297 mm | US 12 | 79% | +1.8 mm |
| US 13 | 301 mm | US 12.5 | 91% | +0.8 mm |
| US 14 | 307 mm | US 14 | 43% | +4.8 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 5mm 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 -5.76mm compared to -0.96mm 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 snug/narrow.