Product Description LASCO Plumbing Specialties 17-6189 is a 5/8-Inch Compression Brass Cap. Compression Cap, for compression fittings/systems. Lead free brass construction. Lead free approved product in all states. Used with plastic and copper tubing. 5/8-Inch compression. From the Manufacturer LASCO Plumbing Specialties 17-6189 is a 5/8-Inch Compression Brass Cap. Compression Cap, for compression fittings/systems. Lead free brass construction. Lead free approved product in all states. Used with plastic and copper tubing. 5/8-Inch compression.