Self-Sealing Washers come in metric sizes.
Press Release Summary:

Available in M8, M10, and M12 sizes, SEELOC® Self-Sealing Washers are made of 300 series stainless steel with profiled and ribbed silicone rubber section molded onto one side, creating high-pressure seal to 100 psi. Products are UL Recognized and rated to IP66/68 for Type 4X and Type 6 enclosure protection. Capable of handling temperatures from -160 to +500°F, washers are resistant to salt water, acids, weather, sunlight, ozone, and other hostile conditions.
Original Press Release:
New Metric Sizes Added to Air and Liquid-Tight Self-Sealing Washers Line
Englewood, New Jersey, USA - APM HEXSEAL has announced the expansion of their Metric SEELOC® self-sealing, high-pressure washer line, to include metric sizes M8, M10, and M12. These popular metric sizes have been added to satisfy the increasing national and international demand for this industrial-grade sealing washer line. APM is experiencing a surge of metric size requirements from OEM's who are building marine, medical, military, instrumentation and a broad range of electrical and enclosure equipment throughout the world.
The SEELOC® washer platform is built with 300 series stainless steel -- a uniquely profiled and ribbed silicone rubber section is molded onto one side (facing down) creating a high-pressure seal to 100psi.
SEELOC® are UL Recognized and rated to IP66/68 for Type 4X & Type 6 enclosure protection, and are resistant to salt water, acids, weather, sunlight, ozone and a myriad of harsh, hostile conditions. They can easily handle temperatures from-160°F to +500°F.
The APM self-sealing fastener line has been sold for more than 50 years under the following trademarks:
SEELBOLT®, SEELSKREW®, SEELNUT®, SEELRIVET® and SEELOC®. APM fasteners are sold by leading electronics and industrial distributors throughout the United States, Canada and worldwide. For name and location of nearest distributor, visit the APM web site, www.apmhexseal.com.