Is this product right for you? This outside micrometer boasts a measurement range from 0 to 25mm. Measurement can be taken all the way to 0.01 of a millimetre accuracy. Use it for a precise measure of brake rotor thickness or any flat, cylindrical or spherical objects. Knowing the name of each part will help you understand your micrometer. The frame is the base of the whole tool, with the spindle, and the anvil at the top. The ends of the spindle and anvil form the measuring faces. The sleeve is the part which displays whole and half millimetre measurements. The thimble rotates around this as the spindle moves in and out. On the end is a ratchet and a locking lever sits on the side of the frame. Before taking a measurement, its important to clean the measuring faces. Gently close the micrometer on a clean piece of paper, then slowly pull it out. Now twist the ratchet until the spindle touches the anvil, and the ratchet clicks. The mircrometer should measure zero here, but if this is not the case lock the spindle firmly in place and use the included wrench to rotate the sleeve until the zero lines up. Now that its cleaned and zerod, its time to take a measurement. Place the item to be measured in the frame of the tool and rotate the thimble until the spindle nears the surface to be measured. Now use the ratchet to close the spindle in until the ratchet clicks. At this point, you can take the measurement or lock the spindle, remove the micrometer and then read the measurement. The top row of markings on the sleeve are whole millimetres, the bottom row are half millimetres and the markings on the thimble are one hundredth of a millimeter. To determine an accurate reading, take the number of whole millimetres, add the half millimetre if applicable then add the number on the spindle. Place a drop of machine oil on the spindle once in a while, keep it safe from knocks in the nifty little storage case and your ToolPRO Outside Micrometer will deliver accurate measurement for years to come.