Howell Metal linesets are manufactured to the highest quality standards. The copper tubing is manufactured in accordance with ASTM B-280 standards and specifications and tested in accordance with ASTM E-243 standards. The insulation is tested in accordance with ASTM E-84 standards and specifications. We anneal our tubing in the straight length form prior to insulating and coiling, insuring the most flexible line set available with no kinking during installation.