The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

CUSIP No. 29272C103

NAMES OF REPORTING PERSONS/I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS

(ENTITIES ONLY)

Stephen R. Rizzone

CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

(a)  ☐         (b)  ☐

SEC USE ONLY

CITIZENSHIP OR PLACE OF ORGANIZATION

United Stated

NUMBER OF

SHARES

BENEFICIALLY

OWNED BY

EACH

REPORTING

PERSON

WITH

SOLE VOTING POWER

1,764,234 (1)

SHARED VOTING POWER

0

SOLE DISPOSITIVE POWER

1,764,234 (1)

SHARED DISPOSITIVE POWER

0

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

1,764,234 (1)

CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES  ☐

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

5.22% (2)

TYPE OF REPORTING PERSON

IN

Includes (i) 585,970 shares of common stock held directly by the Reporting Person; (ii) 524,744 shares of common stock subject to options held by the Reporting Person that are exercisable within 60 days of December 31, 2019; (iii) 503,520 shares of common stock issuable to the Reporting Person upon the settlement of restricted stock units (“RSUs”) that vest within 60 days of December 31, 2019; and (iv) 150,000 shares of common stock subject to performance stock units (“PSUs”) held by the Reporting Person that are issuable upon the earlier of (a) the attainment of certain performance goals or (b) his retirement.

Based on 32,616,128 shares of common stock outstanding as of December 31, 2019, as reported by the Issuer to the Reporting Person, plus (i) 524,744 shares of common stock subject to options held by the Reporting Person that are exercisable within 60 days of December 31, 2019; (ii) 503,520 shares of common stock issuable to the Reporting Person upon the settlement of the RSUs that vest within 60 days of December 31, 2018; and (iii) 150,000 shares of common stock subject to PSUs held by the Reporting Person that are issuable upon the earlier of (a) the attainment of certain performance goals or (b) his retirement, all of which are treated as converted into common stock only for the purpose of computing the percentage ownership of the Reporting Person.

CUSIP No. 29272C103

Name of Issuer:

Address of Issuer’s Principal Executive Offices:

Name of Person Filing:

Address of Principal Business Office or, If None, Residence

Citizenship:

Title of Class of Securities:

CUSIP Number:

Not applicable.

Ownership

Amount Beneficially Owned:

Percent of Class:

Number of shares as to which the person has:

Sole power to vote or direct the vote:

Shared power to vote or direct the vote:

Sole power to dispose or to direct the disposition of:

Shared power to dispose or to direct the disposition of:

Ownership of Five Percent or Less of a Class

CUSIP No. 29272C103

Ownership of More Than Five Percent on Behalf of Another Person

Identification and Classification of Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person

Identification and Classification of Members of the Group

Notice of Dissolution of Group

Certifications

CUSIP No. 29272C103