I bought this for the 32 oz container that fits perfectly and securely in the center of my vitamix pro series 300. I am now in the habit of leaving the tamper in the little hole on the top of the vitamix lid during blending, a tip I learned on the internet. No food flying out yet. It works well that way for me, mixing nicely. I have made mainly smoothies so far. I find this a vital tool for the 32 oz container .