I found this Mark 42 helmet on Thingiverse and I thought that it was really cool. After printing it I found that it was sized way too small to wear and there were several problems with it. I took it into Tinkercad and fixed as many of the problems as I could. I added a chin extension slide to try and make the opening big enough to put your head through. It goes together in three parts, the tongue piece slide into the larger piece and the small block gets glued onto the very end to stop the tongue from sliding out again. I also added a lot of touch up details to make it more durable. I haven't actually printed it full size yet so there may need to be a few more adjustments, for example, the opening may need to be widened still. Hopefully everything works as intended though, enjoy.