I am an engineer and a musician. These are great shakers, well built & very sturdy. Plastic does not mean they are not sturdy! The entire line of Meinl Luis Conte Double Shakers is superb by every measure. Red is softest & smoothest, Silver is loudest and hardest, Black is in-between. Pretty simple, just dial-in the ones that you want. The grey (stadium) model is very loud and more coarse than the others; if using them for recording go with the red (likely the best for recording) or perhaps the black. If you are playing live, these are good and loud and really cut through other things on stage (but a bit more coarse)!