Review on Efficient Doweling Centering Woodworking Accessories for Precise Transfers by Doug Hook

This is metric but advertised as imperial. It's tight, but you'll never be able to move the dowels. If you drill a 3/8 inch diameter hole, the anchor will not fit. To use this you will need metric drill bits and anchors which are hard to find in the US. I'm sure they work fine for metric dowels, but that's not what they advertise.