The eco 9 is basically the evo 9 but longer to accommodate an extra baffle. Both are sealed cans while the Tirant is the user serviceable variety.Yep, remove piston and booster spring then screw in the 3 lug mount. I always thought that the only pistol can that AAC offered a 3 lug mount for was the Tirant series. I'd have to do more research on the Eco