The UK's new fiver has won many fans since it was launched in September.
It's tough. It doesn't tear. You can spill beer on it, put it through the washing machine and it will survive to buy another round.
But one thing it turns out it's not, is fat-free.
Because it turns out the plastic polymer it's made from also contains small amounts of tallow, derived from animal waste products - and some vegetarians are not happy.
Familiar to previous generations as the base for every day staples such as soap and candles, tallow is traditionally derived from beef or mutton (but sometimes pork) at the slaughterhouse or later in the food production process.
Vegans and vegetarians faced with this revelation have taken to social media to voice their concern and over 40,000 people have signed a petition calling for the contents of the notes to be changed.