The size of your pool in gallons = 4000
If your pool is an AG (above ground) or IG (in ground)= IG
If it's IG, tell us if it's vinyl, plaster/pebble, or fiberglass=PEBBLE
The type of filter you have (sand, DE, cartridge) and, if you know, the size, model number or flow rate of the filter.=150...