Don't bother. Spend a little more. Be happy.
I'm sold on Castelli. Fits me perfectly, performs nicely. One sad exception -- Ergo Tre Knickers.
I've worn them less than 10 times -- outside stitching on the seat pad is coming undone; outside fabric covering on the seat pad is fraying. Looks like I may get 3 or 4 more rides out of them before they blow up.
I bought them at $75. At that price it seemed like a screaming deal. Before I bought them I called customer service and asked the tele tech "what am I giving up" at this price. The answer: nothing. The reality: very poor quality.
If you want something you can wear once or twice a year, what the hell. If you live in an area like I do where you need knickers or full tights 4 or 5 months of the years, spend a little more. Get something that will last you a couple of seasons.