Sturdy, Sturdy, Sturdy. I love these. I bought 2 sets so I could 3 compressors per coil. These are so well built, and so well designed that I'd have no hesitation using just a set of 2 on a coil. I use 3 per coil so I can manipulate the spring along 3 axes for alignment/reassembly reasons. Some people complain that they fall apart; that the thrust bearings fall apart. Well, mine have been through plenty of use and show no signs of wear. I am willing to bet that those people complaining neglected to pack the bearing with red high pressure grease before using. All bearings will fail without lubrication; especially those subjected to thousands of pounds of spring load. Grease the heck out of the leadscrew, the bearing, and the telescoping pipes, then sit back and watch these things make compressing springs look easy.