Based on our experience in AR building , it appears we're always in search of small parts that seem unimportant, until they are, because we can't find any. Our AR15 detents and small parts kit composition reflects our experience, it includes the following (1 of each unless otherwise specified):
Take down / pivot pin detents (x4), KNS stainless steel, nitrided. We've lost our share of these tiny spring loaded missiles, so we include extras ( it's cheaper than fitting a GPS on them).
Bolt catch plunger
Bolt catch roll pin (not pictured)
RBF (Reinforced buffer retainer pin)
Trigger guard roll pin
Safety detent (x2), KNS stainless steel, ntirded. Safety detents should be considered wear items, so we include an extra.
RBF is a billet machined 17-4 buffer retainer, heat treated to H900, with a 10% larger diameter tip.
Reasonably priced with shipping included, we think it will make many AR owners happy :)