ECWCS Generation 3 Level IV Windbreaker, "New OCP," USGI/RFI Issue. 

This jacket is not insulated -- it is meant to serve as a windbreaker, on top of other insulated layers (Level 1-2-3).

Shell Layer: Designed to be worn with base and insulative levels in transitional environments to provide wind and sand protection.

The Wind Jacket is designed to act as a low volume shell layer that optimizes the moisture wicking properties of other GEN III insulative and next-to-skin layers. It is also designed to be worn under body armor. Constructed from stretchable nylon with a water resistant finish, this full-zippered jacket provides wind and sand protection with low weight and bulk.

OCP has 15 NSNs (all of which fall under LIN J05015).  MultiCam (the older pattern) is also available, under LIN LIN E95531.