porta nailer

Hi All, I need some advice on the correct size cleats to use on my recent purchase of a Porta-Nailer? This is the model here. https://www.nailfastonline.co.uk/00083/Hardwood-Flooring-Nailers-and-Staplers/PortaNailer-402-Flooring-Nailing-Kit-T-Form- I am laying 18mm solid oak boards from...