My 380 has a 4mm shaft, because the collet I have goes off center when I tighten the allen screw and must be a 5mm. I can't afford to buy a bigger motor now and wanted to try the 380 first. I ordered the collet from Allfield. According to the site it says "Your order has been successfully processed! Your products will arrive at their destination within 2-5 working days." I don't know how that is possible, but we will see.
Thank you and sorry to be a pain.