This is a brass screw in thermostatic cartridge for 3/4" and 1/2" shower mixer valves.For detailed technical measurements for this cartridge, please take a look at the tech diagram in the photos section above.Technical Information and MeasurementsTotal Cartridge Length (including thermostat element): 103.7mmLength of cartridge from top of spline to bottom of brass body (hexagonal nut): 101mmNumber of teeth on top spindle spline (which the temperature handle connects onto): 20Width of top spindle spline (which the temperature handle connects onto): 7.5mmNumber of teeth of second toothed spline (which the temperature stop ring connects onto): 45Width of second toothed spline (which the temperature stop ring connects onto): 20mmDiameter of screw thread: 35.8mmDiameter of top O'ring: 34.5mmDiameter of middle O'ring: 34.5mmDiameter of bottom O'ring: 34mmNumber of O'Rings: 3Material: BrassType: Screw inGauze Filters: 2Wax Element: Vernet (France) (at the bottom of the cartridge on the wax thermostat element, it will read . Vernet . France . ).The thermostatic cartridge will generally need replacing the shower is not regulating water temperature correctly. This could mean the water temperature won't get hot, won't get cold or fluctuates. The thermostatic temperature handle can also seize or become stiff when the cartridge needs replacing.The aesthetics on this model of cartridge can change over time, for example, the build at the bottom of the cartridge can change. This does not affect compatibility in any way.Another example of this change is that the markings on the cartridge can change. Some have no markings apart from the Vernet France at the bottom, others might have numbers on them, for example, 10 and 15, and others might have a code like m8, m10 or m15.If you can't find the thermostatic cartridge which you're looking for or want to clarify you have the correct one, simply go to our Find a shower part page, upload a photo of the part you have and we'll tell you what part you need to order.This cartridge may also have the markings m1, m2, m3, m4, m5, m6, m7, m8, m9, m10, m11, m12, m13, m14, m15, m16, m17