The Armsreach Universal Co-Sleeper® can Co-Sleep Twins together right from day one. Of course it is perfect for singletons too. It attaches to any bed width, from single to California King. Like the Original, the Armsreach Universal Co-sleeper shares the same benefits, uses, conversions and safety features. It attached to the parents' bed in exactly the same way. It is fully tested to the UK standards and European Standards.