I believe you are refering to the smaller vest, machine, that can come with a chest vest as opposed to the older full black vest. My 'two cents' I tried the blue chest vest and didn't like it. It almost made me aggitated and didn't seem to clear me out, my chest felt funny and I got a sore throat from it. I also wasn't sure how it was helping if it wasn't all over. I have heard differing opinions from CF institutions, some say it is good others say it isn't. I thought I had also heard, CFers were getting the fuller vest, not the small chest one. Now as far as the machine itself, I like the size and the ability to move it without the grunting as before. But I must say they aren't perfect. I have gone through three in two months, the first one lasted nine months, and since the replacements haven't been so great. Makes me a little nervous to leave town with it.