Universal rotary hop up kit. R/Flat/Reg arms/nubs

Please read or you will not understand how to use this kit. It is not drop it, you may have to cut spots that are marked and sand spots for some clearance for some hop up units. This is an advanced kit for people who are skilled with hop-up and accuracy mods. Due to the challenge of this kit the markup price is much much lower than my drop in kits for other hop-ups. It is only a $2 markup of the cost of any of these kits with any material.

It's intended for hop ups with rotary adjustable wheel in the back, and a arm with a normal 2mm pin in the middle. It has four slots for this pin so you can set the arm forward or back.

The back has 4 holes for a 1mm pin, you can set what height the pin interacts with the wheel. Ideally it should be level with the wheel slot when the wheel is half-way turned. The pin should fit snug in the hole of the arm and then only go into the wheel slot 1.5 to 2mm when the arm is level. When it goes up or down it will pull it out some, but kinking becomes more of an issue the deeper it is in the wheel slot. You can use any metal 1mm wide snippet for this, but a long M1 screw or mini nail will likely work best. Most wheel slots are 1.4mm wide so it should be fine. You can glue it into the arm at you own risk. The back of the arm has two spots to cut if you need to shorten the back and move the entire arm backwards using the 2mm side holes.

IMPORTANT:
Once the back 1mm pin is set you may have to angle the bottom edge below the pin so it doesnt hit and max out the arms movement, there is no mark for this so be careful. You can also just shorten the back of the arm too if you run into this issue, but it will have less support.
Always try to move the whole arm around before cutting anything off and double check for other workarounds first.

The front arm has 7 groves for the nubs to pivot it, there are 3 arms with diff depths of these groves marked L M S. There are also 3 extentions for them as well. The nubs use one of these groves to pivot in, if the arm is too long on the front end there are spots to cut it shorter.
I also included 4 traditional nub holder attachments that allow you to use regular nubs. Those are NOT ment to hold the nubs included with this kit! They are for if your are using a Laylax or Maple nub for any reason.

​If you are doing a Flat hop you may need to use the deeper depth arm and an extention to hold an included nub deeper to the bucking/packing. You can glue an extention with super glue or something tacky such as thread lock if you wish to remove it later.

There are 3 width varants of this kit. 4mm, 4.2mm and 4.4mm. Real Prowin/Dytac hop ups are 4.2mm, clones are typically 4.4mm. I have drop in kits for 4.2mm for Prowin/Dytac M4 hop-ups that will work fine for 4.4mm clone hop-ups in my shop. But this kit is for any other uses that are more odd.

Look at the arm and see if its remotely like yours, if so messure the inside and pick one of the 3 widths and read the specs below of the lengths.

The back hole edge is 3.3mm or 1.3mm if cut from the back of the arm.
The front hole edge is 8.5mm or 3mm if cut from the front of the arm.
The whole arm is 17.4mm long or 9.8mm if cut all the way on both ends.
Short nubs included are 4.2mm long nubs included are 6mm long but can be cut.

You need to center the nub on the window/patch before you put the arm ontop of it, if the nub is too long or off center (forward and back) it will kink the nub and mess up how the kit should work. Look into your window to see if the hopping surface pushed in the barrel window from the kit is even from front to back.

This kit is very precise, more than casted plastic parts, do not try to sand the sides of the nubs and arms, or their contact surfaces. If you need a more narrow kit or even wider please PM me here.

This kit isnt for krytac hops as their arms have the pin on the front. Maxx hop-ups already have a wonderful arm kit so they dont need this kit, however they have feeding issues due to loose tolerances.