Review on Tranz-X Jump Seat: Cable-Less Dropper Post - The Ultimate Riding Companion by Oren Perry

This seems like a good solid product but you have to be very careful to measure the clearance before you buy it or you'll only lose $100. When installed in the seat tube, this dropper post is a full 4 inches high from the top of the seat tube to the top of the seat rail clamp, so your saddle will be at least 6-7 inches higher than the top of the seat tube. when the post is fully collapsed. In other words, in the lowest position, it's like lengthening a regular seatpost by about 4 inches. You can't use 100mm of dropper travel unless the top of your seat is a whopping 9 or 10 inches above the top of the seat tube in its highest position. Look closely at my eyedropper image at the very bottom and compare it to the stem spacing on your bike. It's my fault but I was very disappointed to find that I can only drive with the seat all the way down - that thing doesn't do me any good.