I prefer Wiseco in my own personal ski's, due to them being forged and their lightness, but for cast pistons I like Pro-X and Vertex.
Both the Pro-X company and the Vertex company in Italy are divisions of the P.M.I. group. ART makes pistons for the Pro-X company. Pro-X and Vertex pistons both have identical ART and Yamaha designation codes inside of them just like OEM pistons(also made by Art) do. All from the same molds. They also used the same RIK(Riken company) ring sets.
Some people on here may not be familiar with Vertex pistons that I am a dealer of.
These high quality pistons are manufactured in Italy, and are priced competitively despite their exotic origins.
The company started in 1953 and is the leader in Italy and in Europe for Powersports pistons production, with as customers the most important OE companies and Racing Teams in motorcycles, go-kart and marine ranges.
Piston skirts are Molybdenum Bisulphide coated for faster break in and increased piston life. All pistons are heat treated with a T5 hardening and tempering cycle.
Vertex Pistons are race proven to be a strong and hi performance piston.