Siren is a shimmery pen.  Medium blue, pink and a pale aqua green all swirled together.  The shimmer dances around the pen with light!  
Material is by Turntpen Co
Model shown is Gemini ♊️ 
This is an example of the material and not the actual pen u will receive.  **Please specify model and nib preference in Notes when ordering** EF F M B BB 1.1 1.5