Convex (Model A) spherical crown densitometer which is helpful when establishing spacing standards in forest thinning and determining light requirements for regeneration. Features a mirror reflector engraved with a cross-shaped grid of 24 quarter-inch squares to delineate a plot overhead. Slightly offset convex so your head does not appear in grid. Walnut instrument case 75x75mm. Built-in levelling bubble. Operating instructions included.