This Grip-Rite hammer tacker is built with the professional in mind. Whether it is insulation, carpeting, roofing, felt paper or poly sheeting, these rugged tools can take any abuse you give them. The GRR11 uses staples with a crown of 3/8 in. and lengths of 1/4 in., 5/16 in. and 3/8 in. It is also compatible with A11 Arrow T50 staples. The GRR11 is rear-loading for speed and ease. Grip-Rite stands behind this product with a 90-day warranty.