The Opus 88 Flow fountain pen is a large eyedropper-filled pen with a piston operated shut-off valve. The barrel is made of transparent acrylic with playful colored swirls and a solid colored resin cap and features a silver stainless steel Bock nib. The Opus 88 Flow Fountain Pen is a great choice for anyone who values a high-quality writing experience and wants a pen that is both functional and stylish.