Do not buy. This thing is dangerous. I made a rack and it worked fine. Following the instructions, I made a second frame and compressed the spring. Some clamp in the gut broke off. Compressor guts collapsed. Now, as I write this, I've been compressing a spring in this piece of shit sitting in my vise. He will not be fired. I call the company and of course nobody answers. So I gotta get my pen out somehow without killing myself. I liked you, I read reviews and even saw videos of people using it. I thought it should be ok. Not correct!