Hi, I am looking for a follow focus ring, seamless would be nice but not necessary.  I want the ring to have a snug fit on a pre-36 Iscorama housing (a tad less than 3" wide)  I would appreciate any input, I'm a newbie to videography, I'm using a Nikon D800 on a Red Rock micro cinema deluxe rig.  Cheers,  Nate