These have an expander wedge similar to the handlebar stem. If you look under the seat at the top of the seat post, there is a bolt head. You will likely have to remove the seat to get a wrench on it. First estimate how far you need to move the seat. Loosen the seat clamp bolt and remove the seat from the seat post. Next, loosen the bolt on top of the seat post. If the post doesn't move, back the bolt out about 1/4 inch and smack it with a hammer to loosen the wedge. Make sure you are holding onto the post so it doesn't drop into the frame when it breaks free. After the post is loose, adjust it to your desired height and tighten the bolt on top. Replace the seat and check your adjustment. If still too high or too low, take the seat off and start over. It is a good idea to grease the wedge, bolt, and post while you have it out of the frame for future adjusments. If the post isn't stuck and you can find the right wrench, you can make adjustments without removing the seat.