Basis of presentation and significant concentrations and risks (Tables)

3 Months Ended

Mar. 31, 2019

Basis of presentation, significant concentrations and risks [Abstract]

Schedule of Sales Concentrations by Major Distributors

The Company sells its products primarily through approved distributors in the People's Republic of China (the "PRC"). The Company's sales are highly concentrated. Sales to distributors individually exceeded 10% of the Company's revenues for the three-month periods ended March 31, 2019 and 2018, are as follows:

	For the Three-Month Period Ended March 31,
	2019					2018
	US$		%			US$		%
Distributor A, located in PRC		56,499,732		18.7	%		47,731,909		15.4	%
Distributor B, located in PRC		33,931,975		11.3	%		29,867,832		9.6	%
Distributor C, located in PRC		32,491,923		10.8	%		35,567,286		11.5	%
Distributor D, located in PRC		21,968,499		7.3	%		32,353,013		10.4	%
Total		144,892,129		48.1	%		145,520,040		46.9	%

Schedule of Cash and Cash Equivalents

Cash and short-term restricted cash mentioned below maintained at banks consist of the following:

	March 31, 2019		December 31, 2018
	US$		US$
Renminbi (“RMB”) denominated bank deposits with:
Financial Institutions in the PRC		505,806,079		366,773,172
Financial Institutions in Hong Kong Special Administrative Region ("Hong Kong SAR")		8,134		8,134
Financial Institutions in Dubai, UAE		59		-
United States (“U.S.”) dollar denominated bank deposits with:
Financial Institution in the U.S.		6,131		40,390
Financial Institutions in the PRC		17,052		17,050
Financial Institution in Hong Kong SAR		39,299		131,892
Financial Institution in Macau Special Administrative Region ("Macau SAR")		6,095		6,144
Financial Institution in Dubai, UAE		581		14,464
Hong Kong dollar denominated bank deposits with:
Financial institution in Hong Kong SAR		156		156
Dirham denominated bank deposits with:
Financial institution in Dubai, UAE		329,725		438