Tiny screw M2.5

a) It is a standard that defines the specifications for cross recessed raised cheese head screws (Pan Head). These screws have a raised cylindrical head with a flat bearing surface and a cross recess, often referred to as a Phillips drive (Type H). Some other common types are cross recess type Z (Pozi) and Generic hexalobular socket / 6 lobe. 

a) DIN 966 refers to a standard for countersunk raised head screws with a cross recess drive (commonly Phillips or Pozi)

b) The screw head is partially countersunk but has a domed or raised top, providing a semi-flush and decorative appearance.

a) ISO 7380-2 specifies the standard for hexagon socket button head screws with collar. Generic hexalobular socket (6 lobe) is another common alternative used in various applications. 

b) This screw features an extended cylindrical tip, known as a dog point, at the end of the threaded portion, enabling precise alignment and positioning in mating components.

Serretions under head / Extremely short length

Thin hexagon head 

Nylok blue patch