These are made to OEM specifications.
They do not raise or lower the Compression Ratio.
8.8:1 compression ratio (factory)
Piston (84.50 mm, +0.50 mm Over)
Part # 11 25 1 714 810
One purchase is for 6 pistons with rings as pictured
Compatible with BMW E30 M20 Late Model 2.5 engine
MAHLE Original pistons are OE quality and have many premium OE features. Pistons have to put up with extreme pressures, as their working conditions have become significantly tougher in recent years.
Naturally, the demands on pistons have also risen progressively: they must be lighter, must have lower oil consumption and must be absolutely safe and reliable.
Once purchased these can not be returned.