We have the quick change set at work up to 2" I wish I knew about these back when I was contracting as they are the cats meow for knocking out holes in cabinets as long as you have room for a drill, the first time I used it I couldn't believe how smooth it cut, and there is a ridge to keep it from going all the way into the cabinet, the pilot bit has a slightly larger cutting head so the slug doesn't hang up on it as there is a spring that pushes the slug back out of the hole saw and you just pull it off the pilot bit, they also cut very fast and we use a little cutting oil on them when we use them for stainless steel cabinets, I have never used a faster cutting hole saw on stainless which in the steel mil most of our box's and disconnect are.
I was sure they were made by Kline as they are in a black/dark gray plastic case which has 6 cutters ?" thru 2" with 3-?" pilot bits, and the quick change mandrel that has a ?" hex shaft, I just couldn't find them on the Internet anywhere or on Kline's web site, the picture below is a Greenlee but is exactly the same shape, number of cutters, and the quick change is the same kind, but with the case being a dark charcoal gray or black it doesn't seen like it is, I will try to get over to the tool room to check it out when I go in Tuesday, I know the manager of the tool room told me they cost over $500.00 per set but he could have been quoting the list price?, maybe they are Greenlee but as with Kline I couldn't find the set we have on the net, and the fact the case was not Green like most of Greenlee cases are.
But even at $500.00 to me they would be worth it for the way they cut and how long they last and if you do allot of stainless then they would be a must, and they are faster then using a knock out punch
This is exactly what they look like, this is a photo of the 1" one
Note the ridge at the back of it that keep it from going all the way into the cabinet and hitting something.
I will say that for tight places you will still need a good knockout punch set also because you can't always get a drill into some places.