Purchased to install a 2-3/8" round post steel fence in my yard. The magnets are not strong enough to hold the posts as a round post lacks surface area compared to a square one. The weight alone makes it slide down the bar. how long does it last And where can I find replacement rubber bands that size that don't force me to buy a 100-pack? I'd be happy to pay a few euros more for one with stronger magnets. It is a good quality typical Irwin tool.