The Time Series Buying Guide for IIoT is a resource that helps businesses navigate the challenges of managing Industrial Internet of Things (IIoT) data. Leveraging IIoT data can significantly improve operational and business efficiency by providing actionable insights into machine performance, usage patterns, and environmental conditions. However, achieving these benefits requires tools that preserve and enhance the quality of datasets, ensuring they remain accurate and complete. Managing time series data poses unique challenges due to its scale, speed, and complexity, including massive scale, real-time action, and high cardinality. High-fidelity data is crucial for businesses to detect issues early, build accurate analytics, and create reliable models, but failing to address these challenges can result in incomplete datasets that lack precision. The guide offers practical advice on identifying the right tools and architectural practices necessary to achieve high-fidelity data sets and seamlessly integrating specialized IIoT tools into existing architectures and environments.