Cork bark tubes are a valuable addition to any naturalistic setup. They make very effective hides for arboreal species and do not go mouldy in humid conditions. The price is £1.00 per 100g so if you wanted 400g you would put 4 in the quantity box.
Please note that there is a minimum order of 300g as finding smaller tubes than this is pretty much impossible. The average sized tube to fit most spider enclosure is around 200-300g