Column A

Column B

Column C

Column D

Column E

Balance at beginning of period

Charged to costs and expenses

Charged to other accounts

Deductions

Balance at end of period

Valuation allowance on net deferred tax assets:

Year Ended December 31, 2021

$

21,198

$

7,581

$

—

$

—

$

28,779

Year Ended December 31, 2020

$

16,990

$

4,208

$

—

$

—

$

21,198

Year Ended December 31, 2019

$

11,438

$

5,552

$

—

$

—

$

16,990

Allowance for slow moving or obsolete inventory:

Year Ended December 31, 2021

$

100

$

317

$

—

$

(317)

$

100

Year Ended December 31, 2020

$

100

$

521

$

—

$

(521)

$

100

Year Ended December 31, 2019

$

100

$

985

$

—

$

(985)

$

100