Metric is of course the European measurement system, SAE are based on US sizes (so use inches instead of millimeters). This is important as you may struggle to use a SAE tap and die set on a vehicle with metric measurements. If the car is made in the US, it probably uses SAE measurements.If it is a European carmaker, it's probably the opposite. If can look for a set with dual Metric and SAE compatibility of course then you don't have t. Metal Storage Case - More than with many other types of tools, the storage case is an important part of the tap and die set. Frankly, because these sets can come with multiple parts, you do want a case that is well designed to keep all the little pieces well organized and safely stored. This tap and die set is designed to thread cutting: tap is used to process internal thread, while the die is for external thread. They are perfect for most hand threading applications Specifications: Number of Pieces: 110pc Material: Tungsten steel. Electric Products: International Buyers - Please Note: Our electric products are manufactured according to the specifications of the USA/Canada Electrical Standards and Codes. Trust is important to us so we will work with you to guarantee your satisfaction! Thank you for shopping with us! This item is in the category "Home & Garden\Tools & Workshop Equipment\Hand Tools\Taps & Dies". The seller is "geecollections" and is located in this country: US. This item can be shipped to United States, New Zealand, Malaysia, Taiwan, United Arab Emirates, Argentina, Ireland, Qatar, Netherlands, Sweden, Iceland, Belgium, Israel, Italy, Pakistan, Panama, Switzerland, Chile, China, Portugal, Malta, Australia, Norway, Greece, United Kingdom, France, Peru, Denmark, Colombia, Spain, South Korea, Hong Kong, Jordan, Canada, Costa Rica, India, Mexico, Saudi Arabia, Japan, Finland, Brazil, Turkey, Germany, Brunei Darussalam.