As good as it gets.... but make sure it has "shq" on the end
of the name on the TC body.

If your going to put a filter on a UV is better it at least
cuts out most of the UV light. A Skylight was OK on film, but
not needed on digital. A Protector will at least keep the
main element clean. It's impossible to clean a lens back to
it's original condition.

They released one over a year ago! ....
So does that mean the K-5 was discontinued last year?

link

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Aren't you supposed to let it grow first!

Impressive shots Alan especially the Kestrel which is a great
pose and the white background shows the feathers off well

That's just a lot of waffle with no scientific proof
I've posted links before to Lenstip and other sites that have
found no degradation due to UV filters and I have seen improvements
with Tiffen Haze filters on tests that I have done. Lenstip
didn't even rate that particular filter very highly.

You can actually see an improvement on some of the
Lenstip test shots taken with a filter, particularly
in the balcony area.

Some lenses actually incorporate a UV filter in the design. I've
posted links in the past to some Tamron tests.

Perhaps the filters were upside down!

The Huey does that and it's an absolute pain.... nothing but a gimmick!

I've wasted money on about 4 Vivitar 28mm's non of them are
up to even kit lens level. The Pentax K or M 28mm f/3.5's
or A 28mm f/2.8 seem a much better bet.

If you can stretch to it the Sigma II 24mm seems to be a good
lens for around £70.

The 28mm Sigma isn't as good as the 24mm.

I also bought a K2 when they first came out and thought it was a great camera. I was surprised to see in AP that Ivor Matanle's 2006 review that AP's original test was not a total success as the shutter speeds showed substantial inaccuracies

Probably worth getting the speeds checked?