Tuning Full LCS SK-19 Tear Down and ReBuild (Master Class) Video

Hi everyone, can anyone help me?I lost this part of piston ,can anybody give me the the dimensions of this internal part to build one ?
Without it I'm screwed!

View attachment 582501
Yeah, you gotta build it. Next time I have one apart I'll tell you. The square plate is stuck on mine so I can't even fix it.