They are very light, 163 gms, in fact the seatpost comes with a 85kg rider weight limit for XC use !
http://www.xcracer.com/shop/viewproduct.php?productid=183 for the seat post, http://www.xcracer.com/shop/viewproduct.php?productid=165 for the clamp which at 9 gms is amazing !
Im still not sure what I am supposed to do with the dodgy shaped bag the seat post came in though