If the ink of the calligraphy pen runs out, you can unscrew the back of the pen and refill any black drawing ink. Convenient and save money. Suitable for calligraphy practice and artistic drawing, illustration, handwriting, writing, and design. Our calligraphy beginner set uses non-toxic water-based pigment black ink, which is harmless to your body. The felt nib is well-made, leak-proof and non-toxic. The ink flow is and even, very easy to use