Road Fan

There's a distinction here - Brooks leather saddles, S-A leather saddles, Rivet, Berthoud and the rare ressurrected Ideale are leather tops, where the leather is thick enough to be it's own structural base. I'm very familiar with Brooks, S-A, Rivet and old Ideale. I've always thought of these as "leather" saddles, based on early LBS exposure. For these, the weight-bearing is done by the solid leather top.

I'm not very familiar witn the SLR or any of the Fiziks, but many saddles have a plastic, fiber, or composite structural base that is usually molded (here my faves are Specialized models), and some have this base covered with leather or a padded or gel-based covering. An early one was the Unicanitor, and another was sold by Cinelli. I suppose it's reasonable to call the leather-covered ones "leather," but this is essentially different from the construction of the Brooks leather saddles and similar makes. For these covered saddles, the weight bearing is done by the plastic or similarly molded bases, with the leather cover, which is stretched for a smooth appearance, having a mainly tactile and visual cosmetic function.

While both styles could be termed "leather," they are definitely not the same in terms of what the leather does.