I was looking for a precision basket for the 58. After some digging around I found out that this basket is made by one of the major manufacturers for precision baskets. I noticed they don't really say anything about this in the description, but when you look at the basket it has the laser etching of the brand on it along with the Flair logo. I would imagine this is exactly the same as the basket they make under their name only, but I don't have the exact one to compare.
It is flat bottomed and the same size as the stock basket that comes on the 58. Works great, but you will need a capable grinder to get a finer grind so that you can get the proper resistance when you pull your shot. Although the bottom is flat there is no issue getting it to single stream the espresso once you get the shot going. I use it for 18g but it looks like it could most definitely hold a couple more grams comfortably even with the puck screen in place.
Would recommend this basket for anyone looking to get a precision basket for 58mm portafilter. Here's a tip, this one is priced a few dollars less than the one that is sold under the basket brand only. I've also noticed other machine manufacturers have gotten their baskets made by this company so it is no surprise that flair did the same thing.