The "stripe" is a piece of Bubinga. It is sandwiched between 2 maple boards comprising the neck blank. Then the
scarf joint is made and the headstock blank glued into place. The truss rod cavity is then routed from the top. Then the
fret board glued into place and the neck profile shaped.
The bubinga is used to eliminate twisting. Wood, no matter how long it's been since milling, tends to think it's still part of a tree and will move all over the place depending on temperature and humidity. The bubinga is denser than the maple and helps to steady it.
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