Our revenue is primarily derived from the sale of inventory under long-term agreements with our customers. We have determined that individual purchase orders (“PO”), whose terms and conditions taken with a master agreement, create the ASC 606 contracts which are generally short-term in nature. For those sales, which are not tied to a long-term agreement, we generate a PO that is subject to our standard terms and conditions. In instances where our customers acquire our goods related to government contracts, the contracts are typically subject to terms similar, or equal to, the Federal Acquisition Regulation Part 52.249-2, which contains a termination for convenience clause (“T for C”), which requires that the customer pay for the cost of both the finished and unfinished goods at the time of cancellation plus a reasonable profit.

We recognize revenue over time for those agreements that have T for C, and where the products being produced have no alternative use. As our production cycle is typically six months or less, it is expected that goods related to the revenue recognized over time will be shipped and billed within the current year. Less than half of our agreements contain provisions which would require revenue to be recognized over time.

We disaggregate our revenue based on market for analytical purposes. The following table details our revenue by market for the three months ended March 31, 2019 and 2018:

	Quarter Ended March 31,
(In millions)	2019		2018
Consolidated Net Sales	$	609.9	$	540.1
Commercial Aerospace	415.5		382.7
Space & Defense		107.8	90.1
Industrial	86.6			67.3

Revenue recognized over time gives rise to contract assets, which represent revenue recognized but unbilled. Contract assets are included in our Consolidated Balance Sheets as a component of current assets. The activity related to contract assets for the three months ended March 31, 2019 is as follows:

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(In millions)	Composite Material			Engineered Products		Total
Balance at December 31, 2018	$	12.9		$	37.6	$	50.5
Net revenue billed		(1.4	)		4.6		3.2
Balance at March 31, 2019	$	11.5		$	42.2	$	53.7

Accounts receivable, net includes amounts billed to customers where the right to payment is unconditional.