Vent Latch, Plastic With Metal tab:   
Restricts the opening of the window.  
Usually 2 per sash. 
Color: Beige

Measurements:
Base length: 1-5/32 inch
Base width: 3/8 inch
Overall height: 5/8 inch
(See images for additional measurements)

NOTE: Several of these look similar, Please compare sizes, measurements