When choosing your barrel length, you are looking at the length of the barrel itself without the HopUp Unit. We highly recommend to choose the same barrel length that you currently have installed in your rifle to avoid changing your FPS. However, you may choose a length that is slightly above or below the exact length of your current rifle, as small changes won't have a big effect on range or power.

Smaller barrel bores are reducing the total volume of your barrel and thereby can increase the power of your rifle. We have found 6.05mm to be the perfect balance for all types builds of including CQB and long ranges.

ROTARY STYLE HOPUP UNIT
Barrel by itself fits any AEG rifle. Rifles with rotary style hopups usually found on M4 type guns (e.g. G&G, KRYTAC, SPECNA ARMS, G&P, E&C, etc.) can also upgrade the HopUp Unit with our rotary style CNC HopUp.

We have refined the material mix of our R-Hops to withstand cold and warm temperatures as well has hundreds of thousands of shots. Permanently glued into the barrel, we guarantee that the R-Hop patch is going to stay in position and offer free replacements in case of manufacturing defects.

The best way to clean your barrel is by using a cloth and barrel cleaning rod after every game to remove small residue build up.
DO NOT USE Cleaners, Acetone, Alcohols or other thinners. Damages caused to the R-Hop by using the aforementioned substances are not covered by warranty.

R-Hops are designed to lift heavy BBs by increasing the contact area on the BB. The heaviest BB weight you may use depends on the rifle's power and you may follow this general guide: 350FPS ≤ .28g, 400FPS ≤ 0.33g, 450FPS ≤ 0.36g, 5000FPS ≥ 0.36g. You may use heavier BBs which results in slower travel times with greater accuracy at range.  

We currently only recommend the highest grade of G&G Bio BBs which are widely considered the best in terms of consistency, surface finishes, and size tollerances. When using a R-Hop you are magnifying the effects of imperfect BBs and should therefor use only to the highest grades.

The rubbers used in our R-Hops are able to adjust to the exact shape of the BBs that you are using through abrasion. This process is slow and may take more than 5000shots using your match grade BBs mentioned above. During the break-in period you may see inaccuracy, side-to-side deviations or lesser range which will all improve the closer you get to breaking in your new barrel system.