Caldercraft Model Boat Fittings 8105TN 5mm Triple block. Natural.
Sold In packs of 10, these triple blocks measure ((h) x (w) x (d)) 5.1mm x 4.3mm x 3.5mm and are available in natural boxwood.
Equivalent manufacturers part number cross references:
Artesania AL8531
Caldercraft 8105TN
Mantua 37101