Replacement G3 Filters for Ubbink M300 & G400 WITH bypass ONLY. Please message us if you are unsure about which filters you require. For filters that fit the models without bypass, please see our other listings. If you want to be sure which ventilation unit you have then measure the current filter sizes. The filters for a system WITH bypass are bigger than filters for a system without bypass. With bypass around 500mm x 237mm (LXB) Without bypass approximately 415mm x 237mm (LXB) 1 set includes 2 pieces G3 wire frame filters (EN779) 2 wire frame filters approximately 500mm x 237mm (L x W)