The PP350 and PP351 mounts were designed for outdoor use with small-size pendant domes (such as Spectra and DF5 Series), and the PP450 and PP451 are for outdoor use with medium-size pendant domes (such as DF8 Series). The PP350 and PP450 models mount to parapets, while the PP351 and PP451 models mount to rooftops or other smooth horizontal surfaces. All models accommodate domes that use 1.5-inch NPT pipe. The PP450 and PP451 can be used in applications where mounting and height clearances of models PP350 and PP351 are inadequate. Models PP450 and PP451 are higher by 9.72 inches (24.69 cm) and the overhang is increased by 14.77 inches (37.52 cm).