The Bostitch BTA706-5C 3/8" Staples Heavy Duty 5,000 pack are designed for construction use projects, with heavy duty stapling jobs such as insulation, carpet under laying and roofing felt. The color-coded packaging makes size and product selection easy. These are heavy duty steeel staples with 27/64" Narrow Crown Width - fits Stanley; TR110, TR150, TR150HL, TR250, TRE550, TRE650 series, PHT150, PHT250 PHT350 and Arrow; T-50.