These hollow balls from Play, Italy have been designed to give the juggler more control over the behaviour and weight of their stage balls. As empty balls they are a little too light to juggle (30g) but simply fill them with sand or seeds to your desired weight and you have a customised Russian Ball. The shell to these balls are very firm and each has a slight seam. Each ball comes with a colour co-ordinated silicone plug to keep the contents safe and secure. We've tried using these with water inside too, and whilst it was kept secure, it doesn't juggle quite as nicely as the Sil-X range. Still a lovely idea from the designers at Play.