Radix 325s are perfect for the T-rex 450 and similar sized helis.  In T-rex terms they are 325mm length (tip to tip) 315mm bolt hole to tip (standard blade measurement). 

They are a great balance of lift and control rate.

For an aggressive 3D setup we recommend running at full control extremes (maximum pitch range and cyclic ranges). 

This will give a lively yet very stable feel. 

Even in hard 3D they remain quiet and are hard to overload with extreme controls.