Yep - engine mounted. I bought them, (after reading several posts here I knew I wanted frame mounts,) as they are called "frame sliders" on PJ's site. I took them to my shop a few days before I was to pick up my new 919 for mounting. When I arrived they were engine mounted and I was ticked but my shop, who are very experienced, showed me all the options and they could not figure out why they are called "frame" as the only way they could be mounted, with the parts provided, was on the engine. I emailed with PJ Parts a bunch and they were very nice but basically said that my shop must not have known how to mount them. I requested that they put a clearer photo on their site (the one they show for the 919 is actually a photo of the 599 set up with the bracket) and also call them "engine" sliders but I see they have not done either yet. So mine are now engine mounted and I am not that thrilled with that but have not changed them out yet.