Hi Jon, they are seat raising blocks, made by jigsawing bits of plastic, drilling the holes, going to the longer bolt shop and buying 8 longer stainless bolts and then fitting them Could probably be made in wood as an alternative but I had the plastic so.............
The previous owner of my bike did it the other way and had a load of spacers fitted to the frame under the riders seat....made me feel like a right midget until I realised