When sourcing T slot milling tools, you must prioritize material composition, typically choosing between Solid Carbide for high-speed precision or High-Speed Steel (HSS-Co) for toughness in interrupted cuts. Pay close attention to the neck diameter and length to ensure clearance within the pre-milled slot. For high-performance applications, look for staggered tooth designs which reduce cutting forces and vibration, and ensure the coating (such as TiAlN or AlTiN) is suitable for the specific workpiece material to enhance heat resistance and tool life.