Summary Used on needle files with a 3mm diameter. Interference fit, must be pressed on or use a rubber mallet and a vise. What I used and did; Monoprice mini, .1325 layer height, 40% infill (not sure if it matters, I think it's 100% anyways because it's so small) 60mm/s. Took about 45 minutes for my slow machine, about 2g of material. Easy cheap handle. There are other files that look nicer than mine, but were going to take about 1.5 hours per handle and more material, so I just designed this quick and easy one. I bought my needle files at Harbor Freight with a 20% off coupon for around $2.50, tax included. Came with 2 sets of 6. UPDATE 2-6-17, when I printed one in ABS with a 0.0875 layer, the hole was slightly too large and no longer an interference fit.