Hydraulic, structural and general wear items
Adapters, fittings, hoses, seals and general hardware. Small parts, but hydraulic fittings in particular deserve more care than they usually get.
Hydraulic fittings
Thread form, size and sealing method all have to match. Adapters that appear to thread together while mismatched on form or seal are a common source of slow weeping leaks, and occasionally of sudden failure under pressure. Confirm all three rather than assuming from the fact that it screwed on.
