Joined: Jan 2009
Posts: 44,139
Likes: 6,366
From: New York, NY, and High Falls, NY, USA
Bikes: 1962 Rudge Sports, 1971 Raleigh Super Course, 1971 Raleigh Pro Track, 1974 Raleigh International, 1975 Viscount Fixie, 1982 McLean, 1996 Lemond (Ti), 2002 Burley Zydeco tandem
OK, allen bolts.
Stems almost universally used 6mm in both the expander bolt and the handlebar binder bolt.
Nearly all seat binder bolts were 5mm.
Water bottle cage bolts are usually 4mm.
Derailleur mount bolts were 6mm, and now they've gone to 5mm.
Most adjusting and mounting nuts and bolts that were regular 8mm went to 5mm when they went to allen.
So if you want to stock up, get 2, 2.5, 3, 4, 5, 6. Also get 8mm for kickstands and crank fixing bolts. Get a 7mm if you think you'll be working on French bikes of the late 70's and the early-to-mid 80's.