The Company disaggregates its revenue from customers with contracts by revenue streams. The Company’s revenue streams are presented in the following table:

	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Single-use products	$	82,823	$	76,399	$	145,088	$	149,177
Multi-use products		62,450		66,594		124,430		129,275
Service revenue		29,923		4,221		63,898		7,892
Total gross sales	$	175,196	$	147,214	$	333,416	$	286,344

Revenue is recognized when control over a product or service is transferred to a customer. Revenue is measured as the amount of consideration expected in exchange for transferring goods or providing services.

Sales terms to certain customers include rebates if certain conditions are met. Additionally, sales are generally made with a limited right of return under certain conditions. The Company estimates these rebates and returns at the time of sale based on the terms of agreements with customers and historical experience and estimated orders. The Company recognizes revenue net of these estimated costs which are classified as allowances and rebates.

The Company does not have any unsatisfied performance obligations for contracts greater than one year. The costs incurred to obtain or fulfill a contract are not material.

For variable consideration arrangements where the transaction price fluctuates based on quantity, the most likely estimated quantity is assumed using forecasts provided by the customer.

In most single-use product sales, a quantity is ordered and manufactured according to the customer’s specifications and typically only one performance obligation is included. The Company also manufactures early phase product that can be included in a contract with services. These services are distinct and separated from the product performance obligations and are shown as a service revenue stream. The products are manufactured exclusively for a specific customer and have no alternative use. Generally, under these customer agreements, the Company is entitled to consideration for progress to date that includes an element of profit margin. To the extent an agreement did not include an element of profit margin for progress to date, it would be recognized at a point in time. Revenues that are recognized over time utilize a measure of progress toward satisfaction of the performance obligations. The Company measures progress using an input method which compares the cost of cumulative work in process to date to the most current estimates for the entire performance obligation. The raw materials are excluded from this measurement due to the high value and inclusion in the early stages of the project that would otherwise overstate progress to date.

The Company’s multi-use product sales can be sold to multiple customers and have an alternative use. Both the transaction sales price and shipping terms are agreed upon in the contract. For these products, all revenue is recognized at a point in time, generally when title to products and risk of loss is transferred to the customer based upon shipping terms. These arrangements typically include only one performance obligation.

The service revenue stream represents services provided to a customer to assist with early stages of the regulatory approval process. The customer owns the drug details and process. The Company works with its customers to develop, validate and document the production process in order to comply with the regulatory approval process. These custom development projects could have one or more performance obligations with no alternative use. The contracts are structured to ensure the Company is paid for in-process work, including a profit margin. Revenues related to this stream are recognized over time by allocating to each performance obligation the best estimate of the standalone selling price of each service. Standalone selling prices are generally based on the prices charged to customers or based on an expected cost-plus margin. The Company measures progress using an input method which compares the cumulative work in process to date to the most current estimates for the entire performance obligation.

The timing of revenue recognition, billings and cash collections results in billed trade receivables, contract assets (unbilled receivables), and contract liabilities (customer advances and deferred revenue). For each reporting period presented, the Company reports contract balances in a net contract asset or liability position on a contract-by-contract basis. Contract assets are recorded when the right to consideration is conditioned on something other than the passage of time. When an entity’s right to consideration is unconditional, the receivable is recorded within Trade receivables on the balance sheet. Contract liabilities represent advance payments from customers, and deferred revenue. Contract assets will convert to trade receivables or cash and current contract liabilities will convert into revenue within a one-year period.

Payment terms can vary by the type and location of the customer and the products or services offered. The term between invoicing and when payment is due is not significant. For certain products or services and customer types, payment prior to satisfaction of a performance obligation can be required, and results in recording a contract liability.

	2019			2018
Balance as of January 1,	$	33,490		$	51,896
Contract assets acquired		4,243			-
Revenue recognized from performance obligations satisfied		155,225			145,820
Transferred to trade receivables		(95,848	)		(89,551	)
Currency impact		(388	)		(1,082	)
Balance as of June 30,	$	96,722		$	107,083

The Company recognized in revenue $7,197 and $1,114, during the six months ended June 30, 2019 and 2018, respectively, for which the contract liability was recorded in a prior period.