Guest ed - Basically the whistle is a 'transposing instrument' so you
finger it as per the dots and it plays in the key the whistle is tuned to . So IF the dots are 'C' the Bflat plays Bflat ,if the dots are 'G' the Bflat plays Aflat and so on .
Reference earlier question on Generations , it seems to me that the low price means that there is negligible quality control - Get one that DOES work and it will be a good whistle , but a lot of the mouthpieces are absolutely USELESS .