Tonic Studios - Nuvo Aqua Flow Shimmer Pen - Opal Quartz. A superb companion to the Aqua Flow range. The versatility of the brush nib is ideal for adding subtle opal shimmer glitter effect for details or large shimmering areas to your designs. By combining with the Aqua Flow Pens, you can bring your vivid watercolour pictures to life with a little extra glamour. This pack contains one single pen that has a reservoir complete with a non-drip valve, so simply adjust the pressure to control the amount of liquid released.