Specification: 100% brand new!!! Diameter: 18mm Easy to install This is a replacement for your master brake reservoir sight glass. Comes with the proper gasket for sealing in the brake fluid. Fitment: Universal. This will fit the majority of old Honda, Suzuki, Kawasaki, lots of dirt bikes, Harley's and many other brake cylinders. It can fit your front or rear brake cylinder as long as its 18mm. Installation: 1) Completely remove old sight glass including metal ring and rubber gasket. Be sure the reservoir is drained of all brake fluid and has been washed. 2) Place the rubber seal in the sight glass hole. 3) Gently press the sight glass piece in to the hole. 4) Cover the face with a soft cloth or towel to prevent damage and carefully tap into place with a hammer. Check to make sure the face is flush and even with the font face. 5) Fill with brake fluid, bleed the brakes, and get back to riding safely! Note: 1. Please check the size measurement chart carefully before making payment. 2. Please allow 0.5-1 inch difference due to manual measurement.(1 inch=2.54cm) 3. The color of the actual items may slightly different from the listing images due to different computer screen, thanks for your understanding. 4. Master brake cylinder is not included.