Universal Rite Fit 15" 2.5kW Flo Thru Titanium Heater (27 J0413 3T K) invensys The 17 32 inch cross section gives The 17 32 inch cross section gives this O ring practical value because some extra large groove designs require exceptionally substantial sealing mass for proper fit and compression A part like this is useful because it helps frame and support the skimmer opening 5kW Flo Thru Titanium Heater (27 J0413 3T K) is engineered for Universal Rite Fit replacement applications and helps return the spa to stable The 15" format helps preserve the intended plumbing alignment and equipment bay fit when replacing a compatible original assembly