# Production and dock-to-stock time Production time is how long it takes to build. Dock-to-stock time is how long it takes to arrive and become ready to ship once it's built. Both live on the bill of materials, in whatever unit makes sense: minutes, hours, days, weeks, or months. Add them together and that's the lead time your product page shows. Change either one and every lead time built from that bill of materials updates immediately. ## Questions **Why two numbers instead of one lead time?** Building something and getting it from the supplier to your shelf are different clocks, often with different bottlenecks. Keeping them separate makes each one easier to fix when it's wrong.