Leupold PR Fun
The Mark 4 PR line is a new moniker for the previous "Tactical" line. Great optics and great value.
Basically, they took the VariX III scopes and made them Tactical by (drum roll please.....) replacing the "Gold Ring" around the objective with a "Black Ring"
Then they finished the exterior in matte black (more ooooh's and ahhh's).
They use the standard target knobs, they need the 1/16" allen key to loosen the 3 allen set screws in order to re-index or readjust the zero after you've sighted in the scope.

Many people love this setup.
Couple of criticisms from an old fart (my 2 cents worth)...
During the 200 meter deliberate stage (Match 1) at NSCC this July, my elevation turret spun loose (them 3 allen set screws came loose

) This happened just after I dialed 2 MOA UP from my 100 yd zero and began my 2nd sighter. My scope was the Mark 4 PR 4.5x14x50mm or the VariX III Tactical, whatever you would like to call it.
Luckily, the MARLANT Navy team were able to run back 100 meters to fish out a set of allen keys from one of their many toolboxes. All this was sorted out just before the next match, 200 m Snap match, by then I learned to hold over a bit and salvage a 41-0X score in Match 1
The Mark 4 M1 (tall knobs) only need ONE 3/32" set screw to be loosened and then the turret knob spins freely and easily so that you can re-index the "0" to where you need to do so. The 3/32" set screw is such an improvement especially with gloved hands on cold range days.
I'm not getting younger and I've used these Leupold Standard target turrets for the past 10 years in hunting, Service Rifle , and Sniper Rifle environments. I need 1X reading glasses these days and the little writing on the target turrets drives me to start drinking (again).

So I switched optics to the Mark 4 M1 knobs and life is easy to read the numbers without reading glasses.
In conclusion... I don't want to sound prescriptive and start telling CGNutters what they should buy. Just realize what will work for you and yer budget, and yer eyes, and yer tool set and your level of grief tolerance.
Hey, at least I got a couple of mildly humourous stories to tell about the Leupold Standard Target turret knobs.
I hope this insight helps your shooting game.
Cheers,
Barney