This plastic cradle is for 2" faux wood and vinyl Venetian blinds that use string ladder. It is commonly seen in Levolor brand blinds sold at Lowes. A tag inside the blinds may read PWLD2530. Or, your blind could read "Manufacturer: CF-5." 

This cradle has two rollers and is used on blinds that do not have holes punched in the middle of the slats. This style of blind is called "privacy" or "routless." 

White plastic.

Sold individually.