Caldercraft Model Boat Fittings 8103SN 3mm Single block. Natural.
Sold In packs of 10, these single blocks measure ((h) x (w) x (d)) 3.6mm x 1.9mm x 2.4mm and are available in natural boxwood.
Equivalent manufacturers part number cross references:
Artesania AL8511
Billing Boats BF767
Caldercraft 8103SN
Corel AMNB100
Mantua 37001