Imagines are the best quality and most absorbent prefold I've tried. The Imagine brand is only available through Nicki's Diapers.
We use the "Smart Fit" small size. They were still too long to use in the one-size diaper covers on the small setting. I had to fold them sideways and still fold over the end a little. Now that we're on the second row of snaps in the Best Bottom diaper covers, they actually fit the way you would expect.