5. Segment Information Our Chief Operating Decision Maker allocates resources and evaluates performance at the divisional level. As such, we have determined that we have three reportable segments: Olin Brass, Chase Brass, and A.J. Oster. Olin Brass is a leading manufacturer, fabricator, and converter of non-ferrous products, including sheet, strip, foil, tube, and fabricated products. While primarily a processor of copper and copper alloys, Olin Brass also rerolls and forms other alloys such as stainless steel, carbon steel, and aluminum. Sheet and strip is generally manufactured from copper and copper-alloy scrap. Olin Brasss products are sold primarily to customers in building and housing, munitions, automotive, coinage, and electronics / electrical components. Chase Brass is a leading manufacturer of solid brass rod in North America. Chase Brass primarily manufactures solid rod in round and other shapes, ranging from 1/4 inch to 4.5 inches in diameter. The key attributes of brass rod include its machinability, corrosion resistance, and moderate strength, making it especially suitable for forging and machining for products such as valves and fittings. Brass rod is generally manufactured from copper or copper-alloy scrap. Chase Brass produces brass rod used in production applications for building and housing, transportation, electronics / electrical components, and industrial machinery and equipment customers. A.J. Oster is a processor and distributor of copper and copper-alloy sheet, strip, and foil, aluminum sheet, and coated aluminum products. A.J. Oster operates eleven strategically located service centers in the U.S., Puerto Rico, and Mexico. Each A.J. Oster service center reliably provides products at quick lead-times in small quantities. These capabilities, combined with A.J. Osters operations of precision slitting, hot tinning, traverse winding, cutting, and special packaging, provide value to a broad customer base. A.J. Osters products are sold primarily to customers in building and housing, automotive, and electronics / electrical components industries. Corporate includes compensation for corporate executives, corporate office and administrative salaries, and professional fees for accounting, tax and legal services. Corporate also includes interest expense and income, state and federal income taxes, certain overhead costs, share-based compensation expense, gains and losses associated with certain acquisitions and dispositions, unrealized gains and losses on hedging activities, and the elimination of intercompany sales and balances. The Chief Operating Decision Maker evaluates performance and determines resource allocations based on a number of factors, the primary performance measure being adjusted EBITDA. Adjusted EBITDA is defined as net income attributable to Global Brass and Copper Holdings, Inc., plus interest, taxes, depreciation, and amortization (EBITDA) adjusted to exclude the following:  unrealized gains and losses on derivative contracts in support of our balanced book approach;  unrealized gains and losses associated with derivative contracts related to energy and utility costs;  impact associated with lower of cost or market adjustments to inventory;  gains and losses due to the depletion of a last-in, first out (LIFO) layer of metal inventory;  refinancing costs;  restructuring and other business transformation charges;  inventory step-up costs related to acquisition accounting;  specified legal and professional expenses; and  certain other items. Each of these items are excluded because our management believes they are not indicative of the ongoing performance of our core operations. Below is a reconciliation of adjusted EBITDA of segments to income before provision for income taxes: Three Months Ended March 31, (in millions) 2019 2018 Net Sales, External Customers Olin Brass $ 172.3 $ 178.7 Chase Brass 146.3 171.6 A.J. Oster 111.7 121.5 Total net sales, external customers $ 430.3 $ 471.8 Intersegment Net Sales Olin Brass $ 36.0 $ 21.4 Chase Brass - - A.J. Oster 0.1 - Total intersegment net sales $ 36.1 $ 21.4 Adjusted EBITDA Olin Brass $ 13.9 $ 14.0 Chase Brass 17.0 18.6 A.J. Oster 5.7 5.7 Total adjusted EBITDA of operating segments 36.6 38.3 Corporate (7.1 ) (6.0 ) Depreciation expense (5.6 ) (5.1 ) Amortization expense (0.1 ) (0.1 ) Interest expense, net (4.0 ) (4.3 ) Net income attributable to noncontrolling interest 0.1 0.1 Unrealized (loss) gain on derivative contracts (a) 3.3 (2.4 ) Specified legal / professional expenses (b) (1.3 ) - Lower of cost or market adjustment to inventory (c) 2.8 0.9 Step-up costs from acquisition accounting - (0.2 ) Income before provision for income taxes $ 24.7 $ 21.2 (a) Represents unrealized gains / losses on derivative contracts. (b) Represents selected professional fees for accounting, tax, legal and consulting services for merger and acquisition activity. (c) Represents the impact of lower of cost or market adjustments to domestic metal inventory.