The Brooks handgrip grip consists of many rings of saddle-thickness leather, stamped out of offcuts, held together by three short bicycle spokes and two big, solid, cast ali end caps which provide further location on the handlebar; the centre hole in the leather rings is a pretty tight fit already. The leather doesn't have any perceptible give under the hand, nor has mine shaped itself to my fingers over the three or four years I've had these grips. I use these grips with plain leather dress gloves, lined with silk in summer, cotton in the change-seasons, and wool in winter, no gel. These Brooks grips are just kinder to my hands than the excellent Herrmans of Finland ergonomic gel grips I used before, which are fitted by quite a few upmarket Continental makers (and are cheap enough to cut off when you change something on your handlebars, rather than bugger around with a bicycle spoke trying to get the grip off whole).
The other surprising thing, which I discovered before I switched to a bike designed around 60mm balloon tyres, when I still rode on on hard, harsh, knobbly high pressure 38mm Marathon Plus (yes, I know, by comparison to a 19mm tyre with double the pressure, Marathon Plus are the lap of luxury, but the comparison is with the biggest of the Big Apples, and the most forgiving of those, the unwired folding Liteskins at that), was that the Brooks leather handgrips, which I bought for aesthetic purposes and because SJS had them on sale, offer an added margin of damping even at the high stage to which my bike (which was designed from the ground up around its suspension) is developed.
I don't pretend to know definitively how the Brooks grips work the additional margin of vibration damping I've noticed, but suspect it is by friction between the many rough side to smooth side junctions, aided by some microcompressibility in the edge-on direction. I rode a bike with fancy cork grips the other day and they definitely had more give than the Brooks... However, for such hard grips the Brooks work surprisingly well. I don't need to be able to explain how they work to decide that I won't be giving them up.
For those inclined to try them, the Brooks grips are in the same price range as the expensive ergonomic gel grips Thorn recommends. I think the Brooks are a better deal and more in keeping with a steel touring bike. Be careful though when you choose your colour. The leather edges are raw, and the leather will soon get dirty or, if you wear leather gloves, leech some colour from them. I bought the honey ones because my saddle was honey, soaked them in neatsfoot oil to give them the same non-Brooks brown (a sort of a dark tan) as my saddle, and then used them with my normal black leather gloves. They soon leeched enough black to make themselves darker than the saddle, though with wear the saddle is now getting towards the same shade. (If you use your bike for showing, even sometimes, you need a spare unused honey saddle and pair of grips!)
Andre Jute