Note 4 – Inventories

Inventories are measured at the lower of cost or net realizable value. The cost of inventories is based on the weighted-average principle, and includes expenditures incurred in acquiring the inventories, production or conversion costs and other costs incurred in bringing them to their existing location and condition. In the case of manufactured inventories and work in progress, costs include an appropriate share of production overhead based on normal operating capacity.

Inventories consist of the following:

Obsolete inventory charged to product cost of sales was $96,302 and $219,701, during the three months ended September 30, 2019 and 2018, and $98,349 and $251,984 during the nine months ended September 30, 2019 and 2018, respectively.