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The Parts and Accessories Encyclopedia


MK23 users have always traditionally found various methods to improve the contact between the hop arm and the hop up rubber. For example, by creating mods with rubber wire, inside of pens and pieces of card to improve the shape of the mound and the amount of spread pressure applied to the rubber.


Eventually Airsoft parts manufacturers developed upgrade parts that achieved the same or better effects without the need for DIY modifications to the stock hop arm, using just a single upgrade part to accomplish it. These upgrades came in the form of hop nubs that were direct drop in kits and worked very well with the stock hop arm.

As new hop rubber designs were developed alongside new BB weight categories, so too were new hop nub designs invented in order to keep the an effective and constant contact and pressure with the BB's. We now see specific MK23 hop up nub designs being made available within the community.

Please find below a list of the communities most recommended aftermarket Hop Nub upgrades. Hub Nubs on this list have been tried and tested in Airsoft skirmishes over several months and have proven to remain durable and reliable in use for the tested period.



| Hadron Airsoft Designs H-Plate |

3D Printed

Game changer

Essential item

Confusing to install

Excellent results





The Hadron Airsoft Designs H Plate is available from the following retailer:

logo (1).png

Hadron Airsoft Designs H Plate - Link

Wide Concave Contact


Precise Fit

Plug and Play


  • Shaped for perfect fitment with the stock MK23 hop arm.

  • Strong and durable 3D printed filament.

  • Direction markings.

  • Wide concave underbelly for ideal usage with R Hop mound hop rubbers.

  • Ideally suited for use with the Maple Leaf hop up rubbers.

  • Compatible with stock MK23 barrels.

  • Best used with the Hadron Airsoft Designs TDC cover.

  • Allows for the improved lifting of 0.45 and up heavyweight BB's.

  • Cheapest option on the market.

  • Widely available.

  • Incredibly easy install.


Born out of pure invention and necessity to overcome a weakness in the MK23 platform, Hadron Airsoft Designs entered the MK23 community as a overnight household name in 2016 with their now famous and for many, essential TDC cover upgrade part. Since their arrival, they have continued to provide innovation after innovation for the MK23 community and their MK23's. In this case, the "H-Plate".

The H-Plate was designed as a natural successor to the Maple Leaf "I-Key", which was adopted by MK23 users in conjunction with the use of Maple Leaf GBB hop rubbers and barrels. The "I-Key" however was never a natural fit and often required a lot of setup before functioning to a reasonable level. The H-Plate improved on the design of the I-Key, increasing the width of the concave contact area as well as the width of the part for seamless fitment between the standard hop arm and within the hop assembly itself.


With these additions, the H-Plate nub can be installed in minutes and augments the MK23's ability to hop heavyweight BB's to record breaking distances. For many MK23 users, it is without a doubt a "must have" part.

HAD H-Plate


| Maple Leaf I-Key |

Precise Concave Contact

CNC Construction

Precise Fit

Narrow shape

Not specifically for MK23

Difficult to setup

Effective when setup

Can be expensive





The Maple Leaf I-Key is available from the following retailer:

Maple Leaf I-Key - Link

As part of the Airsoft Taiwan brand, Maple Leaf have an excellent reputation for high quality pistol and sniper rifle upgrade parts. Their inner barrels, hop up replacement units and hop up rubbers are some of the most well received parts in the industry and used widely by bolt action and competition pistol shooters alike whilst still being affordable. Their "Key" hop up parts come in various shapes and sizes to fit different hop up systems.

Manufactured using CNC Aluminum, the Maple Leaf I-Key gets its name from its distinctive I-shape design to allow it to directly drop-in between the hop up rubber bucking and hop arm adjustment plate. The concave underside of the I-Key applies a wide and even pressure across the bucking mound to achieve optimal performance.
The I-Key was designed to be used with Maple Leaf Hop Rubbers using Diamond or Autobot contact patches.


Whilst very effective when used with the MK23 hop arm, the I-Key can sometimes be difficult to install before a sweet spot is found, however, once set up correctly, the I-Key can help the MK23 lift 0.45g BB's or higher to ranges well over 50 meters. For many users the I-Key is still a reliable upgrade.


  • I-shaped design to allow for fitment beneath the hop arm plate. 

  • Strong CNC Aluminium construction.

  • Concave underbelly for ideal usage with R Hop mound hop rubbers.

  • Designed for use with the Maple Leaf Diamond / Autobot hop up rubbers.

  • Compatible with stock MK23 barrels.

  • Best used with the Hadron Airsoft Designs TDC cover.

  • Allows for the improved lifting of 0.45 and up heavyweight BB's.

  • Widely available.

Maple Leaf I-Key


If you know of or have used an aftermarket part that you believe should be listed here, please feel free to submit a recommendation for review.

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