Kong stainless steel quick links are high quality and made in Italy.  The 8mm and 10mm are not only CE rated but UIAA rated.  The 12mm is so overkill there is no point in certifying it.  The 4mm and 6mm are not "certified" but their working load limits are reliable.  Pro tip: you will generally get more strength if you wrench it down.  Alpine Savvy has a great article about what sizes are appropriate for what use cases.  

Available in 4mm, 6mm, 8mm, 10mm, and 12mm.