I love the extreme range but after about 6 brushes they all have the same prob, the bristles on the ends start going on an angle which then makes it hard work getting into the corners. I hope this is up for improvement Alex?
Bristle strength and longevity is often about the design of the brush rather than the bristle material themselves.
The bristle material in the Xtreme range is exactly the same as in our Super-Lite range (and indeed the same as most other brands). However the robustness and longevity of the Xtreme range is far less than the Super-lites mainly due to stock design and density of bristle placement. A Super-Lite brush can often get 12 - 24 months life due to its design - whereas an Xtreme brush used in a tough environment can start to deform after just 2 months. Many Xtreme users get longer than this, but even so the top end of life on an Xtreme brush is about 5 months. The upside is that they are only 110g which is less than half the weight of any other brush on the market.
We are working on a new Xtreme brush which will be more robust - it will probably weigh in at about 10g heavier but should last longer - it is a fine balance with weight and longevity. We are also nearly finished with out testing on the mid-weight brush - halfway between the Xtreme and the Super-Lite that still has 7 rows of bristles and the same footprint as the Super-Lite, but far less weight.
Hopefully the new ranges will have brushes to suit all tastes and working preferences.