Sanford uni-ball gel impact rollerball pen refill, bold, black ink, 2/pack refill for sanford uni-ball’s gel impact provides an ultra smooth ink flow. The 1.0mm refill features acid free, water resistant and fade resistant ink for thick, vibrant writing. Acid-free/water resistant/fade resistant. larger quantity quotes available. Please call 1-888-978-7759. this product arrives to most customers in 2-3 business days.