I wanted to purchase the Ab attachment when I purchased my Total Gym XLS, but wanted to make sure I was actually able to, and going to use it first. Once I was committed to working out on it buying the Ab Crunch attachment on Amazon was next, Amazon had the best price.None of the other reviewers said they had any trouble putting the attachment on, but I do have trouble lining up the holes to push the pins through. This has to be done every time you work out because the attachments get in the way of other exercises. But it is a small irritation and since no one else mentioned it, probably just my lack of coordination.I have been using the Ab attachment for one month now, and have noticed that it has begun to settle in a little, and now the left unit does wobble a little, but this does not interfere with my using it. I just wonder if this will continue to worsen?However, the results have been well worth the purchase, and as others have mentioned this is the first effective ab work out I have ever done that has not caused stress on my neck or back. Having neck issues this was one reason I ordered the attachment. I am really pleased with the purchase, the results and would recommend keeping an eye on the Amazon site. On the date of my review the price of a new attachment was listed as $125 but I purchased it for quite a bit less 30 days ago.I would not recommend buying one of the used Ab Crunch Attachments from Amazon. I did that the first time around. The attachment should come with a manual and a DVD. All I recieved was the DVD (no Ab Crunch attachment). Fortunately Amazon totally took care of everything.I did have a great experience buying my Total Gym XlS very gently used from a private party saving a whole lotta money. Total Gym just wants way too much for them new.This attachment is for the inexpensive Total Gym widely advertised on TV. It WILL NOT fit the more expensive commercial models, as the side rails are about 1/8" too wide. However, it can be easily modified to fit. I have an eight year old 11000 model, which came with all attachments, except the ab attachment, which wasn't made at the time.The channel on the part that fits over the side rails has a plastic sleeve in it, which keeps it from sliding over the thicker side rails on commercial models. All you have to do is cut the SIDES of the U-shaped sleeve off. Leave the flat bottom portion that contacts the top of the side rail. This can easily be accomplished with a hacksaw blade, or even a serrated bread knife.Next you have to drill a couple of holes in the rails for the attachment pins, which is also an easy job.Note: if you have a newer commercial model, the rails are even thicker than those on my older model, and this remedy will probably not work. However, be aware of the fact that Total Gym makes a very nice one-piece ab attachment which fits newer models (which already have the holes drilled in the rails). They sell it for $180, but I got them to readily come down to $90, which is reasonable.Also, the Total Gym ab attachment works mainly the lower abs, and you can pretty much accomplish the same thing with a $15+ ab roller you use on the floor. It puts slightly more strain on the lower back, but if this is not a problem you might try this. I have both the $12.66 "ab wheel," and the $48.98 "Lifeline USA Power Wheel II," for use when traveling. Both of them do a good job of working the abs, although they don't give you the variety of positions for working the oblique abs, etc. that you get with the Total Gym Ab Crunch.It's a great product and I sure like mine. It is true that the channel under the arm rest is too wide to make a tight fit on my APEX G3 but it simply needs a spacer to fill the gap. I used a pair of non-adhesive felt-rubber "Super Sliders", 2.5" diameter for hard floors. I cut a hole in the center for the pin to slide through. I trimmed off a bit of the circle on one side because 2.5" is a bit too big. The material cuts easily with a knife and will not scratch the rail. A few fender washers could also work. While it is a loose fit without a spacer, once I put my weight down on the arm rests my weight holds it down solidly, but like some others I didn't want to have them so loose.This was a fast shipment, brand new in box as described. Very pleasedI uses this for my core and ab workouts on total gymWhen I first saw the Ab Crunch attachment, I was excited -- until I saw the price. Not sure why the Total Gym site sells these for such an exorbitant amount, but I am glad I was able to find it on Amazon a lot cheaper.I purchased my Total Gym off of a TV shopping channel about 6 years ago for a really great price. It is the Total Gym Elite model and I have a lot of the extra attachments.I have been using the Ab Crunch attachment for a few weeks now and love it! I still do crunches on my Total Gym utilizing the pulley system, but find this to be a great addition to my workout roster.I haven't tried all the different variations yet, as some are pretty advanced. However, the two variations I'm doing are challenging.If you have a Total Gym, this would be a great addition!UPDATE 05/30/2012: I have been using this attachment with my Total Gym for over a year now. My husband says my abs look just as good, if not better, than the women pictured in various fitness magazines. I had my yearly physical last month. When my doctor was pressing on my abdomen, she said and I quote, "Oh my word! Your abs are as hard as a rock!" I cannot say enough good things about the Ab Crunch attachment. Easy to use, but will work your abs like nothing else, and give you really great cut and definition.I got it for my Total Gym XLS expensive, but still better than the Total Gym site.Love this, works great.So I think this is great! Based on what I read on a few sites this didn't work for all models but I wasn't sure so I gave it a try and glad I did.. For Platinum owners, this does not fit exactly, the hitch pins and holes are smaller then the machine has but there are several ways to tweak it, which you can easily figure out to suit your needs. All in all a nice addition..