The 0.156" (3.96mm) pitch is a legacy spacing that matches existing SL-156 PCB layouts — useful for retrofitting or extending an established design rather than starting fresh. The housing is natural nylon (polyamide), free-hanging (in-line) with crimp termination, meaning it sits on the wire side of the connection and mates with a board-mounted pin header of the same series and pitch. The natural colour is the base nylon — no added pigment — which is standard for general-purpose internal connectors where UV resistance isn't required.
The listing explicitly notes that contacts are not included. This is the most common mistake on this part — ordering the housing alone and discovering mid-build that the crimp sockets are missing. The 2-640251-0 accepts TE's SL-156 female crimp socket terminals (typically 20-24 AWG, ordered separately under a different MPN). If you're filling a BOM line for this housing, make sure the matching terminal line item is also on the order.
This receptacle mates with TE SL-156 series pin headers of the same 0.156" (3.96mm) pitch and 20-position, single-row layout. For vibration-prone environments, consider whether a secondary locking feature or a dab of connector-position-assurance adhesive is warranted.