The Pentek US-1500 is an undersink water filtration system. The Pentek US-1500 uses any of the following water filter cartridge sets: D-250, D-250A, P-250, P-250A. The Pentek US-1500 features an Electric Monitor that the Pentek US-1000 does not have. The monitor electronically tracks your water usage and reminds you when it is time to change your filters. The Pentek US-1500 Chemical/Lead System is NSF certified to reduce 43 different VOCs, lead, cysts, mercury, asbestos and chlorine taste andamp; odor. The US-1500 systems comes complete with cartridges, a long reach faucet, and installation hardware. The Pentek US-1500 water filter system replaces the Culligan SY-2650 system. The parts and replacement filters are the same.