The Ibanez GWB1 Gary Willis Signature model was introduced in 1999. Available in natural flat (ntf) or  transparent black flat (tkf) finishes.  The fretless GWB1 neck was 20.5mm thick at the first fret line marker, with 34" scale length and a bolt on All Access neck joint which allowed the easy access to the upper frets.

This model was discontinued in 2005.

The Ibanez GWB1005 Gary Willis Signature bass was introduced in 2009, replacing the GWB105 signature model.  The GWB1005 is hand crafted from start to finish in Japan. There are a few changes from the previous GWB105 model: it has a black-faced headstock which no longer bears a Gary Willis signature. Now the signature is on the back electronics cover (each one is hand signed by Willis). The fretless fingerboard is now high gloss finished rosewood (instead of the GWB105's ebonol). The detachable finger ramp, designed by Gary Willis, is still there.

The Ibanez GWB105 Gary Willis Signature bass was introduced in 2005, replacing the original GWB1 signature model. The fingerboard on the GWB105 was ebonol (phenolic) instead of the GWB1's ebony fingerboard, and it has offset dot position markers. The GWB105 was replaced by the GWB1005 model around 2009.

The Ibanez GWB2 Gary Willis Signature model was introduced in 1999 as the fretted version of the GWB1. The GWB2 was available in transparent black finish only and was discontinued in 2002.

Ibanez introduced the Gary Willis signature 5 string fretless bass (model GWB35) in 2004. It has a double cutaway basswood body with maple neck and ebony fingerboard. The GWB35 has a single SFR-GWB Custom pickup, active electronics and black hardware. The detachable finger ramp underneath the string pickuing area, designed by Gary Willis, encourages players to not "dig in too deep" and allows a more consistent attack with quick recovery time.