Bottom Brackets - same thing as headsets I mention above. Rather than the modern BB30s, I've been using square taper BBs on my builds since they are proven (to me) workhorses, they are 'sealed cartridges' (very few dirt/water problems), the frame I have are built for them, and I can get a real nice one for $30. Only had one fail, and it was easy to replace. YMMV