Uni-ball Liquid Ink Roller Ball Pen Refill - 0.5 mm - Black

This is not an actual AG Spalding refill. Its made by uniball and you definitely see the difference when you write with it. Its not as smooth and has a tendency to spew more ink than necessary. On ocassion when pressing on hard surfaces the refill stops writing at all, until you make few lines in different direction to clean out the ball at the tip.

I think a pilot G2 refill fits in this pen also.