The bolt bumper was brown on the nt10 and nt11 but DYE has changed it to orange now. Call em up and get it.
Brown is still ok on the nt10 but it causes weird bolt issues on the nt11. You can also sand it down yourself to test it if you cant wait for the orange one.
Here is my old brown one shaved down at an angle. You want the oring slightly lower than the metal lip between the red and brown oring.