Hey, I asked this question here a couple years back in vain, perhaps someone knows the answer by now as I`m still puzzled about it. All the piston rings available for water cooled Porsches are for model year 2000 and onward. However, rings for 1997-1999 Boxsters have identical measures to all 2.7 engines: 85.5mm bore, thickness: 1.5; 1.2; 2mm. The cylinder liners are the same Lokasil.
So what`s the difference then ringwise between the 2.5 and 2.7 motors?
For example this one should fit the 2.5 engine also:
https://www.ebay.com/itm/314183325976
Yet, based on the the description they are not compatible.