I used these in a session with some year 10 boys. They found the product a little odd in texture and commented that they were not as 'real' as they would have liked in terms of how they felt. They also found searching for the lumps difficult and in some ways although this helped reiterate the process of checking carefully, for some not finding it meant they were not sure what to feel for.
However it was a great tool to utilise to get the conversation going and to lighten the mood, as well as getting them to feel more comfortable with self examination.
Overall useful resource