Most of it has been said. Thr key is that they deform to your shape. I'm not perfectly symmetrical, my pelvis is fractionally twisted. As a result my left sitbone takes a a little more weight than my right. The Brooks compensate for this - over time, the indentation on the left becomes a couple of millimetres deeper than that on the right, and my weight is diatributed evenly. I have one bike with a synthetic saddle on it, a Fizik Aliante that works pretty well, but nothing suits me quite as well as the Brooks.