Single acting (SA) valve cartridge without emergency. The diameter of the drill bit that fits into the slot is 12.7 mm. It can be combined with different coils of both 12 and 24 Volts (VDC) that have a central hole for housing on the valve cartridge with a diameter of 13 mm. Examples of some coils that can be installed to make it work are: Solenoid - Coil 12 Volts Ø13x40 18W Kostal M24x1 (32212T and 32412T), Solenoid - 12 Volts Coil Ø13x39 with Dhollandia cable (32216T and 32416T). This valve, being single-acting or sealing, blocks the flow of oil in one direction while always letting it pass through the other. When electrically stimulated through the solenoid, it unlocks the flow of oil from the other direction as well. Double seal (DA) valve cartridges, on the other hand, block the flow of oil in both directions and therefore must be energized every time you want oil to pass through. You can recognize a single-seal valve by the tip that is hollow, on the contrary those with double seals that are solid. This cartridge is NOT equipped with an emergency pawl! This is located at the rear and is used in case there is a failure of the electric coil which at that point can no longer open the valve cartridge. If unscrewed, the pawl therefore allows the passage of oil and if necessary, to be able to open the bank or lower it to the ground. If you want a valve cartridge that also has this function, you need to buy item 31104T