Chap, an aftermarket, suppose to be harder(last longer) then factory spec vents. PR stands for Precision Rifle (aka www.prbullet.com) company that markets this vent. Cost is $14 for 6 and being PR is only 1/2 a province away in Manitoba(Canada) it is a logistical choice as much as a cost per thing for me.

BTW your choice in powder my not be the most speediest but who'd argue with your results. I have got a little caught up in the chrony I admit more b/c of curiosity and wowing potential but I'd take 200 fps less and an iddy bitty group anyday over a erratic barn burner. 5744 is a bit iffy here in regards to availability and thus I have spent very little time with it, though I did notice its potential, light kiss back and fouling!!! 4759 is as common as bottled water and gets the savage to where it is intended in terms of performance, other eclipse this powder yet with less pressure and safely. Basically boils down to how much you want to invest, shoot and tinker, though I don't think any critter will ever know the velocity difference if its lungs have been deflated!

Enjoy