Stefan over at TenTech released some new arms for the ZMR250 frame. They are built off the THUG arm design and come in both 3mm and 5mm thicknesses and are made of 3k pure carbon fiber. These arms should be much stronger than the stock arms that come with the ZMR250.
The 3mm version: http://tentech-rc.co.uk/thug-frames/zmr-250-upgrade-arms-121.html
The 5mm version: http://tentech-rc.co.uk/thug-frames/zmr-250-upgrade-arms-122.html
I might have to order a set since I did break an arm yesterday when someone powered up next to me while I was flying about 50-60 feet up and it knocked out my signal and I lost control.