Forged pistons are the first hard part most people buy when an engine is going to see boost, and this section carries forged piston sets for four, five, six, eight and ten-cylinder applications — the Audi 2.0 TFSI and 2.5 TFSI, BMW's N54, N55, S54 and S65, VW's EA888, and the Porsche flat-six among them.
Alloy is the choice that matters most. 2618 alloy tolerates more heat and abuse and is the standard pick for a high-boost or track engine, but it expands more when cold, so it runs looser piston-to-wall clearance and can rattle on a cold start. 4032 alloy is quieter and more stable for a fast street car that still sees daily use. Bore size comes next: order to your block's finished bore, not to the stock bore, and confirm compression height against your rod length and deck height before you commit.
Pistons rarely go in alone. Pair a set with forged connecting rods and wrist pins, fresh engine gaskets and seals, and ARP rod bolts and main studs. The full rotating assembly lives in engine bottom end.