The Mono-rail IV is a fixed bridge used on certain Ibanez electric bass models. It is also referred to as the Mono-rail 4, the MR4, or the MR-4. It replaced the Mono-rail II.
As its name implies the Mono-rail IV bridge anchors only a single string as opposed to most bridges used on basses which anchor all four (or more) of the strings. This allows each individual bridge to be mounted at the ideal location to provide perfect intonation. Because of the flexibility this design affords it is used on multi scale basses with fanned frets, although it is also used on many guitars with traditional straight frets.
The design allows for equalized tension across all strings while isolating each string so that it vibrates optimally without impacting any others. The saddle can be moved fore and aft to adjust intonation using the longitudinally positioned Philips screw at the rear of the bridge. Once adjusted the saddle is locked down using a hex screw to prevent any further movement and assure string vibration is transferred to the body of the instrument.
The Mono-rail IV bridge was introduced for 2005 on the Soundgear Prestige SR1000EFM and its variants. It has since been used on several models in the Soundgear and BTB series as well as on a number of artist signature models.
The Mono-rail IV was superseded by the Mono-rail V, which was introduced in 2015 and was mostly discontinued completely in favor of the new bridge after 2016 except on some signature models on which it continues to be used as of 2026.
Specifications:
- Top-Loading String Mount
- Mounting hardware included
- Sold Individually
Ibanez SKU: 2BB1MR4K
Professional installation is strongly recommended. Improper installation may result in damage to the product and/or instrument.
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