Noodler's Heart of Darkness is a popular permanent black fountain pen ink that comes in a 4.5oz bottle. The bottle has a built-in glass eyedropper so you can easily fill your eyedropper-convertible pens. Comes with a free Noodler’s “Charlie” eyedropper fountain pen. This ink is popular for its very dark color and performance on absorbent paper, particularly its ability to resist bleed through and feathering. If you don't have a say in the quality of the paper you use, this ink is one of the best for you. Noodler's inks are handcrafted, so there may be slight color variations from batch to batch.