The Joseph Kuosac Brompton Telescopic Seatpost Extension in black is a high-quality steel accessory designed specifically for Brompton folding bikes. With a diameter of 31.8mm and a plain seatpost type, this set includes a single seatpost extension that is compatible with Brompton bikes. The sleek black colour adds a stylish touch to your bike while providing a sturdy and reliable seatpost for a comfortable ride. Ideal for riders looking to extend their seatpost for a custom fit or as a replacement part for their Brompton bike.