**Understring Radius Gauges: Fast and Accurate Bridge Saddle Adjustment**

1. **Introduction**
   - Understring Radius Gauges are designed for quick and precise bridge saddle adjustments.
   - They feature accurately radiused arcs on both top and bottom surfaces, fitting easily under strings.

2. **Key Features**
   - **Dual-Surface Design**: Bottom curvature for measuring fretboard radius; top curvature for setting string saddle heights.
   - **Low Profile**: Slim shape allows for easy measurement even with strings on, ideal for matching pickup polepiece heights and setting bridge saddles.
   - **Versatile Widths**: Standard width (up to 2-5/8" / 66.68mm) for 6-string guitars and most 4-string basses; extra-wide (up to 3-3/4" / 95.25mm) for wider string spreads, including 5-string, 6-string basses, and 7-string or 8-string guitars.

3. **Sets Available**
   - **Standard Width, Set of 9 Radii**: 7-1/4", 9-1/2", 10", 12", 14", 15", 16", 17", 20".
   - **Extra-Wide, Set of 9 Radii**: 7-1/4", 9-1/2", 10", 12", 14", 15", 16", 17", 20".

4. **Applications**
   - Ideal for determining fretboard radius, setting bridge saddles, and matching pickup heights to string arcs for optimal playability.