I have got hold of a (secondhand) dream machine. 21.5" iMac, Late 2013, 16GB/512SSD/3+GHz i7. Gutted to discover there is no simple way to VESA-mount (being partially disabled I need to mount it on an arm). I am bitterly disappointed with Apple's choice to push the personal computer in the opposite direction from "user serviceable". I'm going to put all the information I find in this post (seeing as these forums allows retro editing). Apple stipulates the base cannot be removed: iMac (Late 2012 and later): VESA mount compatibility However you can preorder VESA-mount for an extra $40: Buy iMac with Built-in VESA Mount Adapter Several companies have created mounts that attach a VESA plate to the back of the existing mount: iMacMount NuMount VESA VIVO STAND-MACB VESA adapter for iMac (buy on Amazon here -- at time of writing this is by far the cheapest option) This is a horrible/clumsy/fugly solution as the existing base will still be floating around underneath the unit, and also the arm to which I need to attach the unit has a ball and socket joint; this compounded with the sprung hinge joint may create problems. The next option would be to disassemble the unit, gut everything out, detach the base from the chassis and screw in a VESA Mount. However, Apple don't sell this component separately. https://www.ifixit.com/Guide/iMac+Intel+27-Inch+EMC+2639+Stand+Replacement/34185 shows a good hack for a 27" model. Unfortunately the eBay listing for the Mount itself says "It will not work with the 21.5" models, or any 27" iMac models prior to 2013." Furthermore, the component does not seem to be available any longer. However, if only someone were to manufacture the appropriate component, it should be possible to do the same fix on a 21.5" model: if you look at the bottom picture on https://www.ifixit.com/Teardown/iMac+Intel+21.5-Inch+EMC+2638+Teardown/17829 you can see that the mount is not in fact welded to the chassis. One possible option for me would be to get hold of a VESA Mount Version, maybe a broken unit, spares / repair, or just the chassis even, and perform a transplant: either transplant the internals of my existing machine into this and other chassis, or extract the VESA Mount and insert it into my unit. One solution might be to use one of the above mounts, and just hacksaw off the base. I might well end up going for that. Another solution might be to somehow hold the unit in place like the way a clamp holds a test-tube. i.e. Grip it around the edges. But this looks like a really tough mechanical engineering challenge. If anyone is able to further this enquiry, please do reply -- or even edit the original post if the forum allows this. Same goes for me. π EDIT: Hunting for the VESA-mount component finds http://www.macpartsonline.com/923-0703-bag-fg-2pk-vesa-21-5-imac-a1418.html# -- I'm waiting to hear from these people whether this is indeed the correct component. EDIT: It appears I may need three or more parts: googling the iMac model (A1418) together with parts starts to get into the right places. The tricky thing is going to be figuring out exactly what parts I need. ($46) 923–0419 Vesa Mechanism Plate iMac 21.5 MD093LL MD094LL ME699LL A1418 ($28) 923–0420 Vesa Tongue iMac 21.5 MD093LL MD094LL ME699LL A1418 ($62) 923–0421 Vesa Mount Adaptor iMac 21.5 MD093LL MD094LL ME699LL A1418 (=$136) (...thanks to http://www.macpalace.com/imac-21.5-inch-late-2012--page-3.html) I think I need those three parts. Maybe plus some screws & maybe screwdriver. http://www.applecomponents.com/?search_within=1&p=all_items&last_cmp=&last_cat=Service+Parts:+Case+Components:+Uncategorized&s=vesa <-- prices for this site seem relatively reasonable. https://www.macpartsdepot.com/index.php/imac/body-chassis.html?limit=100 <-- silly prices but at least they give pictures of the parts. http://www.macpartstore.com/923-041...-imac-21.5-md093ll-md094ll-me699ll-a1418.html <-- decent looking prices. EDIT: I've just learned from a technician at MacPartsOnline.com that: You would also need the housing with a vesa mount capability. The apple part number is: 923-0425 http://www.macpartsonline.com/923-0425-housing-rear-vesa-a1418.html ... and that unit weighs in at $418. So that pretty much kills it.