The Jupio CNI0026 is the equivalent of the Nikon​ BL-3 Battery Chamber Cover.
The Jupio CNI0026 (BL-3) can be attached to an Nikon EN-EL4 / EN-EL4A (or Jupio BNI0003) battery, making it possible to use an EN-EL4(A) in the following battery grips:

Nikon MB-D10 Battery Grip for Nikon D300 / D300s / D700
Jupio JBG-N002 Battery Grip for Nikon D300 / D300s / D700

Nikon MB-D40 Battery Grip for Nikon D40 / D40x / D60 / D3000 / D5000
Jupio JBG-N007 Battery Grip for Nikon D40 / D40x / D60 / D3000 / D5000