A tubular spare latch, designed for use with the BL5000, BL5400, BL6000 and BL7000 series.
 
The internal variant comes in two different backsets:
2 3/8″
2 3/4″
 
Be advised, by default, the product kits come with a 2 3/8″ tubular latch. If you are unsure on which version you require, the backset refers to the length from the face plate to the spindle follower.