Set screws are a type of screw generally used to secure an object within another object and is generally fully threaded.  Slotted set screws are tightened with a screwdriver; square head set screws are tightened with a wrench.
Unit of Measure
Items
CUP POINT SQUARE HEAD SET SCREW, THRU HARDENED, PLAIN (INCH)

1/4-20 X 1/2 SQUARE HEAD SET SCREW CUP POINT THROUGH HARDENED
Web Price $1,013.67

CUP POINT SQUARE HEAD SET SCREW, THRU HARDENED, PLAIN (INCH)

1/4-20 X 1/2 SQUARE HEAD SET SCREW CUP POINT THROUGH HARDENED
Web Price $24.81

CUP POINT SQUARE HEAD SET SCREW, THRU HARDENED, PLAIN (INCH)

1/4-20 X 5/8 SQUARE HEAD SET SCREW CUP POINT THROUGH HARDENED
Web Price $989.10

CUP POINT SQUARE HEAD SET SCREW, THRU HARDENED, PLAIN (INCH)

1/4-20 X 5/8 SQUARE HEAD SET SCREW CUP POINT THROUGH HARDENED
Web Price $24.20

CUP POINT SQUARE HEAD SET SCREW, THRU HARDENED, PLAIN (INCH)

1/4-20 X 3/4 SQUARE HEAD SET SCREW CUP POINT THROUGH HARDENED
Web Price QUOTE
Diameter N/A 1/4
Pitch N/A Coarse
Length N/A 1/2 N/A 1/2 N/A 5/8 N/A 5/8 N/A 3/4
Material N/A Alloy Steel
Finish N/A Plain
Package Quantity N/A 6000 N/A 100 N/A 6000 N/A 100 N/A 4000