Overview Reviews Product Description Non Return Valve 12mm I.D. Suits 12mm (1/2inch), ID. Snap together, trim to length, 45mm (1 3/4 inch) maximum length. Product Videos Custom Field Product Reviews Write a Review Write a Review × Ronstan Non Return Valve 12mm I.D. Rating * Select Rating 1 star (worst) 2 stars 3 stars (average) 4 stars 5 stars (best) Name Email * Review Subject * Comments *