Treatex | W216 Preservative 2.5LTreatex W216 Preservative is a water based treatment for interior and exterior wood, offering reliable protection against blue stain and fungal attack in timber. Key Features: Protects timber from blue stain and fungal decay Suitable for indoor and outdoor use Ideal for doors, windows, cladding and fences Must be sealed with a suitable topcoat for outdoor use Easy to apply to prepared, dry wood surfaces