IMHO, Value for money wise the SX Multiguard from Essex Enviromental are as good as any, £48+vat for 10, and they're what I use in 9 cases out of 10, but like Ditch says if it's high traffic, use steel. If you do a risk assessment which you will do, even if it is a mental one, not written, and it calls for steel boxes then you should use them, otherwise you will be leaving yourself open to prosecution if non target species get poisoned from a smashed/broken bait box.