If the car is lowered at all, or has bigger wheels fitted, it will go through pattern arms in no time at all. I fitted a £15 quid one once to a car lowered with 17" wheels and it broke in a week

Ford ones are the way forward, even better if you go for the Royal Mail spec ones for the van. They're more expensive though, but stronger still.

Powerflex make bushes for the lower arms too, but get mixed reviews really!