There are so many bite indictors around but none seemed to be as durable as I wanted them to be for the money. It took some time but I have managed to get hold of these which I think for just under £3 each are unbeatable value for money. They have really strong bars and the slider weights stay where you set them...

These weights can also be removed to fish very light (slack lines).

Dove tail quick release brackets, slider weights, adjustable line tension and heads can be unscrewed to add isotopes.