Caldercraft Model Boat Fittings 8105SN 5mm Single block. Natural.
Sold in packs of 10, these single blocks measure ((h) x (w) x (d)) 5.1mm x 2.4mm x 3.5mm and are available in natural boxwood.
Equivalent manufacturers part number cross references:
Artesania AL8513
Billing Boats BF697
Caldercraft 8105SN
Corel AMNB102
Mantua 37011