Signature Platinum series and Bullfrog spa filter cartridge
147mm H x 204mm D x Closed top with D-Handle x Open square thread bottom spigot 58mm OD, 51mm ID (2 square threads 5mm apart)
There are 2 x types:
Standard (1st picture) - No hole in top
Nature2 Cap - Has hole in top for Nature2 cap (If you are not using a Nature2 stick, you do not need the filter with a hole.