✔ Meets/Exceeds: DIN 912
✔ Screw head style: socket cap, head diameter: 5.5 mm, head height: 3 mm
✔ Screw drive system: internal hex drives, also known as hex socket drives, hex size: 2.5 mm
✔ M3 x 30 means : metric screws, thread diameter size 3 mm, thread length 30 mm

[ Sizes ]----[ Thread Length ]----[ Total Length ]
M3 x 30-----30mm/1.18"-------33mm/1.30"
M3 x 35-----35mm/1.38"-------38mm/1.50"
M3 x 40-----40mm/1.57"-------43mm/1.69"
M3 x 45-----45mm/1.77"-------48mm/1.89"
M3 x 50-----50mm/1.97"-------53mm/2.09"

[ Package Contains ]
M3 x 30-----20 Pcs
M3 x 35-----20 Pcs
M3 x 40-----20 Pcs
M3 x 45-----20 Pcs
M3 x 50-----20 Pcs
Hex Key ----1 Pcs

[ About Internal Hex drives ]
Internal Hex drives, also known as Hex Socket Drives, have a hexagonal hole in the center that requires an Allen key, also known as a hex key or Allen Wrench
[ About Socket Cap Head ]
Socket Cap Head , also known as Allen head , have a recessed drive, and are commonly used when there is not enough clearance for a conventional wrench or socket. They are fastened with an Allen wrench, which is also called a hex wrench or hex key