Joytech 3.93'' (100mm) Diameter Spinning Top Base K9 Crystal Glass Concave Mirror, Great High End Transparent Surface Double Concave Top Accessory DZ04

It works acceptably as a spinning top base, but the finishing on the edges of the glass is disappointing. In the pictures it looks smooth and minimalist, but in reality the edges are quite rough with some chipping and discolouration - nowhere near as elegant as advertised. Would suggest buying a vast from a more well-known brand instead…

This is exactly what it says a 100mm diameter concave on both sides glass disk just what i wanted for spinning a gyroscope and messing with light rays but the one i was sent has some chips in the edge not bad enough to ruin the function of the disk but still enough to show poor quality control

I really love this lens and have ordered another one! It is definitely concave on both sides.The glass is very smooth on the top and bottom. More experienced folks with spinning tops have said to use the oils on your hands or face to lubricate the glass. But I do not find the need. You be the judge, however. If you feel the top/bottom of the glass, it's smooth to the very edge. Right on the edge it goes down at an angle and then goes flat on the sides. That part of the lens, and on the sides, are not smooth like the glass on the top and bottom but is safe to handle.With regards to the bottoms of tops, I don't feel there is any danger of scratching the bottoms of the tops because of the way it is designed.Highly recommend!

These polished glass trays are a must for top spinning! Well made and perfect concave design. Can't be much more fun to spinning without them. Highly recommended. I stumbled on them through Amazon recommendations. Choose your own source and price but consider these for adding to the fun of having a spinner top.

The media could not be loaded. Loved everything