About 5 mm in size, I found it sharp and not ground, lying inside below the oil dump hole. I was washing the engine and after dumping wash oil decided to put my finger inside to see if there was anything unusual there (I didn't own this engine before). There was a sharp and large something that felt like a chunk of the piston. Pulled it out and saw it was a glass shader that would fit nicely on a ring or brooch. Is the glass debris in oil better than the metal one? I'm thinking of 3D printing an oil dipstick plug that would be level with the oil sump mouth and would not stay in the way of variator cover.