The MEC Enhanced Tappet Plate spring is the only tappet plate spring officially tested and endorsed by PTS.
The “midcap syndrome” is when an airsoft gun exhibits unnatural fps fluctuations and inconsistent bb feeding when using a fully loaded midcap magazine. This is when the upward pressure of the bb’s from the spring in a loaded midcap magazine pushes the nozzle upwards and out of alignment and causes drag on the nozzle thus preventing it from returning fast enough to consistently load the next bb. One of the culprits in an otherwise fine AEG is usually a weak tappet plate spring. This issue tends to manifest itself more often when using the 250 round capacity PTS EPM1 due to the higher than usual upward pressure caused by the full load compression of the immensely long EPM1 magazine springs.
The MEC Enhanced Tappet Plate Spring has been extensively tested with the PTS EPM and EPM1 use. It is suitable for most standard v2 and v3 gearboxes. It is made of the toughest steel wire and heavy load ability make it a reliable and desirable choice.