Over the years KP has designed and tested countless piston designs on our watercraft engines. To this day, we have tested and built the most reliable, badass engines in the Kawasaki world! Here, we offer the very best we have developed over the years. KP does not use the JE ring pack (JE rings are very hard to seat on Kawasaki watercraft), we have our own rings that we have specifically developed and have manufactured. Our rings are extremely strong, lightweight and have a very thin profile for optimal performance and reliability. No more GIO issues, no seating issues, plus far superior ring sealing! All pistons can be used with stock connecting rods or aftermarket. 15F/SXR/Ultra LX/STX 160 (ALL 1.5L N/A engines) pistons come in 10.6:1 compression (Stock), 12.5:1 (Our recommended stock replacement for 93 Octane ONLY) and our 13.5:1 Compression (For 95+ Octane or E-85). For 250/260 we offer 9.5:1 for stock replacement (93 Octane ONLY!), 10.5:1 Compression (Can be used on 93 Octane in cooler climates, recommended 95 Octane). 300/310 come in 7.8:1 Compression (For a safer than stock setup, if fuel is or was an issue), 9.5:1 Compression (93 Octane required and cannot run additional timing without higher octane fuel to prevent detonation). Other pistons can be made to your specifications. For big bore kits, please see our big bore section.