Swissstop RX Plus Black Cartridge Brake Inserts

I recommend this product

First off - don't be but off by the price - this is for a pack of 4, rather than just a pair.
On the bike, they are excellent - braking is positive, but not too fierce, and remains the same in wet, mud and sand..
They also are non-abrasive, so cut significantly down on rim wear.
I have also used the green pads - which are also extremely good - but are very positive - other people have compared them to "having disc brakes" - so unless you need to stop very suddenly a lot of times, black should be fine.
I would suggest rubbing the surface of the blocks with a fine emery board before use - this prevents the squeaks before they wear in. (This advice goes for any blocks...)