4. Property, Plant and Equipment, net (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property and equipment, gross	$ 52,969	$ 51,558
Less accumulated depreciation	(31,921)	(29,284)
Total property, plant and equipment, net	21,048	22,274
Land [Member]
Property and equipment, gross	1,565	1,565
Buildings And improvements [Member]
Property and equipment, gross	17,834	17,332
Machinery And Equipment [Member]
Property and equipment, gross	31,707	30,670
Vehicles [Member]
Property and equipment, gross	778	778
Office Equipment [Member]
Property and equipment, gross	857	851
Construction In Progress [Member]
Property and equipment, gross	$ 228	$ 362

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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