What size sharp bins do you use? I have a 1 litre one which doesnt take to long to fill but the problem is that the pen needles dnt actually fit in without pushing them and because the needle comes through the bottom bit i could actually prick myself with it. So that isnt very safe. Been to my doctors and chemist and apparently cant get a bigger one on prescription. But the hole you put the needle isnt big enough! What size etc is urs. X