What I think you’ll find is most tungsten jigs using MM sizing. I have seen 3MM, 4MM, and 5MM. My best advice is to go to Kendersoutdoors.com and click on the orange/yellow tungsten jig. They have their jigs compared to a penny there. I think their 5MM with a gulp alive minnow or 4 spikes should be perfect for crappie. I love their prices too!