Hydro-Gear model numbers are located on a white tag on the hydro body.
OEM Hydro-Gear Filter #52114
Fits Models: ZT-2800, ZT-3100, ZT-3200,
ZT-3400, ZT-3600 & ZT-3800
OEM Hydro-Gear Filter # 72537
Fits: ZT-4400
OEM Hydr-Gear Filter # 71943
Fits: ZT-5400
