This ventilator can be installed by piercing or with the self - adhesive ring Cat. No. 42647. Once installed on the film, it continually renews the air inside a boat or damp room. This circular ventilation clip Cat. No. 42647 enables you to take effective action against the continuous formation of humidity, mould or odours for applications such as containment or boat winter storage. This product is sold in packs of 5, supplied in a plastic bag.