A pair of Vent-Axia G4 grade filters for the loft mounted PIV units.
These will fit:
125mm 5" G3 Cone Filter *FOR EXTRACT VALVES*
Brink Renovent HR 250/325 Medium / Large (Without Bypass) replacement Filters
Brookvent Aircycle 1.1, 1.2, 1.3 & 1.3+ Replacement Filter G3 Kit
Domus HRX2D Replacement Filters
Domus HRXC-AF (MVHR air filter (2 pack)