The following table presents our revenues disaggregated by product classification and by operating segment, excluding sales taxes collected and remitted to governmental authorities (in thousands, unaudited).

	Three Months Ended
	December 31,
(Dollars in thousands)	2019		2018
Medical Device
Product sales	$	5,023	$	4,778
Royalties		8,898		7,685
Research, development and other		2,234		2,384
License fees		1,249		2,411
Total Revenue - Medical Device		17,404		17,258
IVD
Product sales		4,952		4,973
Other		260		10
Total Revenue - IVD		5,212		4,983
Total Revenue	$	22,616	$	22,241

Contract asset balances consist of estimated sales-based royalties earned but not collected at each balance sheet date and are subject to timing fluctuations at the end of a given period. The Company’s deferred revenue, or contract liability, is primarily related to the upfront and milestone payments received pursuant to the collaborative license and commercialization agreement with Abbott (the “Abbott Agreement”) for the Company’s SurVeil™ drug-coated balloon product (“SurVeil DCB”) discussed in Note 3.

As of December 31, 2019, the estimated revenue expected to be recognized in future periods related to performance obligations that are unsatisfied for executed contracts with an original duration of one year or more totaled approximately $15.8 million. These remaining performance obligations relate to the Abbott Agreement (Note 3), exclude contingent milestone payments under the Abbott Agreement, and are expected to be recognized over the next six years as services, principally the TRANSCEND study, are completed.