The Mercer & Barker GW5 euphonium mouthpiece is a medium 25.7 mm "5-size" Glyn Williams model designed for players who want a classic British euphonium sound in a slightly smaller, more efficient cup. With its 25.7 mm cup, 7.28 mm throat, and a supportive 6.85 mm rim, the GW5 delivers a warm, singing tone with excellent pitch stability while making the upper register and long rehearsals more comfortable than many larger 4-size pieces
Efficiency and Comfort
This mouthpiece is positioned as a modern upgrade for players moving from popular 5-size mouthpieces. Retailers and makers reference the GW5 directly against models such as the Denis Wick SM5, Wick 5AL, Alliance DC4, and Schilke 52D. The euphonium-specific cup shape and carefully balanced mass help the GW5 produce a rich, centered sound that works in brass band, wind band, solo, and doubling situations without feeling tight or stuffy.
The GW5 combines Mercer & Barker’s focus on comfort, balance, and weight with a versatile medium size that suits advancing students, serious amateurs, and doublers who want a reliable main euphonium mouthpiece. It provides excellent response and clarity across the full range.
Specifications:
Inner Diameter: 25.7mm/1in
Rim Width: 6.85mm/.27in
Rim Contour: moderately wide with rounded inner edge
Throat: 7.28mm/.29in
Cup: Medium shallow
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