Single row of 40-holes, female header.
Can be cut to size with a pair of wire-cutters. Standard .1" spacing.
We use them extensively in the Olimex development boards.
They mate very well with break away male headers.

Please note: You will probably lose one pin with each cut.

Features:

• Receptacle Style: Square
• Number of Pins: 40
• Pin Spacing: 0.1" (2.54 mm)
• Receptacle Depth: 6 mm