I bought one of these in January of 2008, I have known about them forever, but never got around to buying one for whatever reason.
The TF 500 comes in black as welll as clear,and mine is the former of the two; I just don't know WHY I didn't buy one of these before...I have to say that I am very pleased with this item's performance!
Tea-balls are pretty-much going the way of the dinosaur in my tea-making gadgetry dept.!
I have always felt that tea-balls are as cumbersome as they are ineffecient, since the leaves usually expand much, much more than one would expect as has been evidenced by my usage of the TF 500 (you'll be amazed at just how much space your tea will take if you give it the room!), in comparison, the tea would expand in the tea-ball so much so, that it would not permit adequate circulation of the brewing water to the leaves, which means that much of the tea I was using was not actually "yielding" brew, and I was simply wasting precious tea.
I now get optimum yielding of my tea with the TF 500, (using less because of the full circulation around the leaves vs. the "bunching" that occurs in a tea-ball) better flavor, and negligible sediment, the design is smart, the top serves as a stand for the infuser after the brewing is complete, and cleanup is as simple as rinsing under warm water.
I think that the "tarnishing" issues are probably due to the harsh chemicals that are present in automatic diswasher detergent (these can and often include:T.S.P., Chlorine and Sodium Hydroxide=lye), if you must clean it, it was suggested to me that a soft towel and a little bit of baking soda make a good, neutral means of cleaning without harsh chemicals, or the possibility of introducing the potentially lingering flavor/scent of liquid or automatic dishwashing detergents into your infuser, and subsequently into your precious tea; "Dawn Original Gunpowder Green" somehow just doesn't sound very good!
It also bears mentioning that it fits my two-cup teapot(2.5"/64mm opening) as well, it just sticks up on the top, so you may not really need the TF 300.
I didn't mean to write so much about this item, but I felt an "obligation" to spread the word to all who enjoy loose-leaf teas, so if you're sitting on the fence, and are hesitant about this item, I encourage you to purchase it without hesitation...and "no" I'm not employed by the company!
The bottom line is that I wish that I had bought one of these a LONG time ago! I love it, and HIGHLY recommend it....don't waste your time with anything else (like I did!!! :) ).