t.akustik Micscreen flex Mini

Pros:
-It really helps with having your mic focus on the sound you are trying to record without room reflections
-Cheap
-Feels sturdy
-Easy to attach and remove from a mic stand

Cons:
-The only slight con I have is that it is so small that it doesn't work well for higher mic's like the rode NT1-A for example (you can work around this problem by not sliding the foam all the way over the beam but than it easily falls of)

Conclusion:
For the price you cant go wrong. I will never record anything anymore without at least this micscreen behind it.

The downside of using directional (cardioid) microphones is that sound picked up to the rear of the microphone is severely coloured. Obviously, the whole point of a directional microphone is that this sound is heavily attenuated by the design of the polar pattern, but anything that does get through will sound very unnatural.
When recording in a less-than-ideal acoustic environment a screen like this gives the ability to have a second line of defence against that unwanted unnatural sound. The microphone itself will still behave as intended, but spill and reflections can be managed. It is just a curved bit of foam with a slot in it, but it easily fits onto the XLR at the rear of hand-held style of microphone.
Well worth it's relatively small cost.