They are Mahle pistons according to this article.
2007 Toyota Tundra full-sized pickup trucks

Here is their description of the gasoline engine pistons Mahle makes.
Aluminium pistons for gasoline engines

I imagine you could call or email them and ask what they put in the Tundra.

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2007 Tundra 5.7, Double Cab, SR5, Blue Streak

TRD (stickers removed), de-badged, Volant Intake, Zoomers exhaust , Doug Thorley headers, Leer 100R, Bedrug, Curt front mounted hitch, Sirius interface kit, Tekonsha Prodigy brake controller, OEM alarm activation, Wet Okole seat covers, Stubby Antenna, Folding Rear Seat Mod for Double Cab, Unichip