There are many OST to PST converter tools available online, and their performance can vary depending on several factors such as the size of the OST file, the complexity of its contents, and the processing power of your computer. However, some of the fastest and most reliable OST to PST converter tools include:

OST to PST Converter: This is a user-friendly tool that can quickly convert OST files to PST format without losing any data. It also supports batch conversion, which can save a lot of time if you have multiple OST files to convert.

OST to PST Converter: This is another fast and reliable tool that can convert large OST files to PST format quickly. It comes with advanced features like previewing the content of OST files before conversion, selective conversion of mailbox items, and saving the converted files in various file formats like PST, EML, MSG, MBOX, Office 365, NSF, TGZ, PDF, etc.

Softaken for OST to PST Converter: This is a powerful tool that can convert highly corrupted OST files to PST format quickly. It can also recover deleted mailbox items from OST files and save them in PST format.

It's essential to note that the performance of an OST to PST converter tool depends on many factors. Still, you can improve the speed of the conversion process by closing any unnecessary applications, ensuring that your system has enough memory, and avoiding working on other programs while the conversion is ongoing.