Intangible assets, net, consisted of the following (in thousands):

 

Amortization expense was $13.5 million for the Successor period from April 1, 2021 to June 30, 2021 and $0.6 million for the Predecessor period from January 1, 2021 to March 31, 2021. Amortization expense for the Predecessor was $0.6 million and $1.3 million for the three months ended and six months ended June 30, 2020, respectively.

The estimated amortization expense for each of the five succeeding fiscal years and thereafter as of June 30, 2021 (Successor) is as follows (in thousands):