The T50 staple pack set is made of stainless steel, #506SS1 includes 1000 count staples: 3/8’’ crown size, 3/8’’leg length; T50 508SS1 includes 1000 count staples: 1/2’’ leg length. Ideal for heavy duty stapling jobs such as insulation, carpet under laying and roofing felt. Universal fit with ARROW T50, Dewalt, Bostitch, Stanley, Surebonder and other brands that use T50 (3/8''or 1/2'') Staples. Stainless-steel construction designed to resist rust for durability. Rust-resistant finish suitable for wet, non-saltwater locations, not intended for use in marine conditions and harsh saltwater applications.