How to upgrade the shocks on your MN model series using a spring from a cheap biro pen - The pen spring mod.
The easiest and cheapest upgrade to your MN99 Model (any MN series) suspension using a spring from a biro pen. The suspension on an MN99 is pretty shocking and this quick mod will help dampen the bounce and excessive suspension movement for your rock crawler.
The MN model crawler is available from Banggood
