Description Diamine Red Edition Thunderbolt fountain pen ink is a bright shade of blue with some copper sheen. It was released as part of the 2021 Inkvent Calendar, and is now part of the regular Red Edition lineup. The 50ml glass bottle is very unique. Diamine fountain pen ink is considered to be well behaved and smooth flowing, and has been made in the UK for over 150 years. Having trouble deciding between colors? Use our Ink Comparison Tool to quickly and easily view different colors side by side. We offer Free Shipping on all orders over $50 for US customers, and for orders over $250 for our Canadian customers. We offer Free Shipping on all orders over $50 for US customers, and for orders over $250 for our Canadian customers.