When you're scrambling up a Rocky bluff or bounding along a riverbank, the last thing you want is gravel and grit seeping into your Five Fingers. The KSO is and all-new design with thin, abrasion-resistant stretch polyamide and breathable stretch mesh that wraps your entire forefoot to keep stuff out. A single hook and loop closure helps secure the fit. Non-marking xs trek performance rubber soles are razor-siped for sure grip.
| Men's | Women's | Inches | Classic VFF size |
| 2 | 3 | 8" | W34 loose |
| 2.5 | 3 | 8.19" | W34 |
| 3 | 4 | 8.31" | W35 |
| 3.5 | 4.5 | 8.5" | W36 |
| 4 | 5 | 8.69" | W36-W37 |
| 4.5 | 5.5 | 8.81" | W37-W38 |
| 5 | 6 | 9" | W38 |
| 5.5 | 6.5 | 9.19" | W38 |
| 6 | 7 | 9.31" | W39 |
| 6.5 | 7.5 | 9.5" | W40/M38 |
| 7 | 8 | 9.69" | W40-41/M39 |
| 7.5 | 8.5 | 9.81" | W41/M39-M40 |
| 8 | 9 | 10" | W41-W42/M40 |
| 8.5 | 9.5 | 10.19" | W42/M41 |
| 9 | 10 | 10.31" | M41-42 |
| 9.5 | 10.5 | 10.5" | M42 |
| 10 | 11 | 10.69" | M43 |
| 10.5 | 11.5 | 10.81" | M43-44 |
| 11 | 12 | 11" | M44 |
| 11.5 | 12.5 | 11.19" | M45 |
| 12 | 13 | 11.31" | M45-46 |
| 12.5 | 13.5 | 11.5" | M46 |
| 13 | 14 | 11.69" | M47 |
| 13.5 | 14.5 | 11.81" | M47-48 |
| 14 | 15 | 12" | M48 |
| 14.5 | 15.5 | 12.19" | M48 Squeeze? |
| 15 | 16 | 12.31" | M48 Squeeze?? |