Inventory consist of material, labor and manufacturing overhead and are recorded at the lower of cost, using the weighted average cost method, or net realizable value. The components of inventory at December 31, 2019 and 2018 net of inventory reserves, were as follows:

The Company periodically reviews quantities of inventory on hand and compares these amounts to expected usage of each particular product or product line. The Company records, as a charge to cost of sales, any amounts required to reduce the carrying value to net realizable value. The Company recorded a charge to the provision for inventory obsolescence in the amount of $0 and $31,752 for the years ended December 31, 2019 and 2018, respectively.