These are replacement bars for Studio49  Alto and Soprano Xylophones 2000 series. The longest Alto (C) is known as 40 and goes to the the shortest known as 73

The longest soprano note bar is called 52 (C) and goes upto 73 and the shortest (A)

Both Alto and Soprano xylophone use the same style of note.

These replacement bars are for the series 2000G. They are from a man-made fibre/resin called Grillodur. They are a pale brown in colour.