At first glance that looks tiny. Why are you interested in this particular one? I would recommend either the Steeda unit (which I have) or the Mishimoto version. They both look nice and have plenty of coolant capacity.
I like the sleek look of the radium but the less capacity I do not like. I will probably go with Mishimoto. I asked them about the issues with the sight glass and this was their response:
"Thank you for your email. The current design of our recovery tank uses a sight glass whereas previous designs used a sight tube. We have seen a few of the sight tube-featured recovery tanks get a leak at either the elbow/fitting of the tube itself fail. These are easily replaced, but we made a change in the design. The latest design features a sight glass, which we haven't heard of any issues. Hope this helps and give us a call when you're ready to order. We are always here to help and support our customers. Please feel free to follow up with any additional questions or concerns and I would be more than happy to help!"
Here is a picture of my original design Mishimoto tank, so far (knock on wood) it hasn't leaked, and if it does it is an easy fix. The new design is nice as well, the tank is well build and designed. Installation in 10 minutes with no need to drain the old tank.