A19 series is a proprietary 3/8" crown which will fit only Rapid R13, R19, R23, R33 and similar staplers.

These 1/4" length flat wire staples are 3/8" crown. Made of 23 gauge Electro Galvanized steel. Electro Galvanized steel provides a very thin layer of coating with a measure of protection against the elements. Over time these staples may corrode. Not recommended for ACQ Treated Lumber. 

Applications Include:
Insulation, vapor barriers, house wrap and roofing felt.