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 cost of goods during the three months ended June 30, 2018 and 2017 totaled $7,823 and $21,542, respectively, and $32,283 and $21,542 during the six months ended June 30, 2018 and 2017, respectively.