We recognize revenue upon transfer of control of our products to the customer, which typically occurs upon shipment. Our main performance obligation to our customers is the delivery of products in accordance with purchase orders. Each purchase order defines the transaction price for the products purchased under the arrangement. Direct sales to building materials distributors, home centers, direct customers, and retailers represent the majority of our sales. Our standard sales terms are Free On Board (“FOB”) shipping point. We have some sales terms that are FOB destination. At the point of shipment, the customer is required to pay under normal sales terms. Our normal payment terms in most cases are 45 days or less and our sales arrangements do not have any material financing components. In addition, our customer arrangements do not produce contract assets or liabilities that are material to our consolidated financial statements. Within our Architectural Specialties segment, the majority of revenues are customer project driven, which includes a minority of revenues derived from the sale of customer specified customized products that have no alternative use to us. The manufacturing cycle for these custom products is short.

Incremental costs to fulfill our customer arrangements are expensed as incurred, as the amortization period is less than one year.

Our products are sold with normal and customary return provisions. We provide limited warranties for defects in materials or factory workmanship, sagging and warping, and certain other manufacturing defects. Warranties are not sold separately to customers. Our product warranties place certain requirements on the purchaser, including installation and maintenance in accordance with our written instructions. In addition to our warranty program, under certain limited circumstances, we will occasionally and at our sole discretion, provide a customer accommodation repair or replacement. Warranty repairs and replacements are most commonly made by professional installers employed by or affiliated with our independent distributors. Reimbursement for costs associated with warranty repairs are provided to our independent distributors through a credit against accounts receivable from the distributor to us. Sales returns and warranty claims have historically not been material and do not constitute separate performance obligations.

We often enter into agreements with our customers to offer incentive programs, primarily volume rebates and promotions. The majority of our rebates are designated as a percentage of annual customer purchases. We estimate the amount of rebate based on actual sales for the period and accrue for the projected incentive programs costs. We record the costs of the rebate accruals as a reduction to our revenue. In addition, other sales discounts, including early pay promotions, are deducted immediately from the sales invoice.

We account for product shipping and handling costs as fulfillment activities and present the associated costs in costs of goods sold in the period in which we sell our product.

Our Mineral Fiber and Architectural Specialties operating segments both manufacture and sell ceiling systems (primarily mineral fiber, fiberglass wool, metal, and wood) throughout the Americas. We disaggregate revenue based on our product based segments and major customer grouping as these categories represent the most appropriate depiction of how the nature, amount, and timing of revenues and cash flows are affected by economic factors. Net sales by major customer group are as follows:

Distributors – represents net sales to building materials distributors, who re-sell our products to contractors, subcontractors’ alliances, large architect and design firms, and major facility owners. Geographically, this category includes sales throughout the U.S., Canada, and Latin America.

Home centers – represents net sales to home centers such as Lowe’s Companies, Inc. and The Home Depot, Inc.

Direct customers – represents net sales to contractors, subcontractors’ alliances, large architect and design firms, and major facility owners. Only sales to U.S. customers are reported within this customer group.

Retailers and other – represents net sales to independent retailers and certain national account customers, including wholesalers who re-sell our products to dealers who service builders, contractors and consumers. Geographically, this category includes sales throughout the U.S., Canada, and Latin America.

The following tables provide net sales by major customer group within the Mineral Fiber and Architectural Specialties segments for the three and six months ended June 30, 2019 and 2018:

	Three Months Ended				Six Months Ended
	June 30,				June 30,
Mineral Fiber	2019		2018		2019		2018
Distributors	$	161.4	$	156.7	$	306.0	$	294.4
Home centers		21.2		20.5		44.3		44.5
Direct customers		17.5		16.8		31.6		30.5
Retailers and other		14.0		12.7		28.9		28.0
Total	$	214.1	$	206.7	$	410.8	$	397.4

	Three Months Ended				Six Months Ended
	June 30,				June 30,
Architectural Specialties	2019		2018		2019		2018
Distributors	$	37.3	$	33.4	$	68.8	$	61.8
Direct customers		19.0		7.5		32.1		15.4
Retailers and other		1.6		1.0		2.4		1.3
Total	$	57.9	$	41.9	$	103.3	$	78.5