Disciplined Growth Investors (NASDAQ: PRLB) reports 2.5M shares

Rhea-AI Filing Summary

Proto Labs Inc: Schedule 13G/A amendment showing a passive investor position. Disciplined Growth Investors, Inc. reports beneficial ownership of 2,497,355 shares of Proto Labs common stock, representing 10.5% of the class as of 03/31/2026. The filing lists 2,351,815 shares with sole voting power and 2,497,355 shares with sole dispositive power.

Insights

Investor Relations Analyst

Large passive stake disclosed: 2,497,355 shares (10.5%).

Disciplined Growth Investors filed an amended Schedule 13G/A reporting beneficial ownership of 2,497,355 shares as of 03/31/2026. The filing shows sole voting power on 2,351,815 shares and sole dispositive power on 2,497,355 shares, indicating direct control over disposition decisions.

As a 13G filer, the position is presented as passive; subsequent filings would disclose any change in intent or active ownership. Future amendments will reveal whether holdings change materially.

Key Figures

Beneficial ownership: 2,497,355 shares Percent of class: 10.5% Sole voting power: 2,351,815 shares +2 more

5 metrics

Beneficial ownership 2,497,355 shares as of 03/31/2026

Percent of class 10.5% reported on Schedule 13G/A

Sole voting power 2,351,815 shares voting power reported in amendment

Sole dispositive power 2,497,355 shares dispositive power reported in amendment

Signature date 05/15/2026 signed by Chief Operating & Compliance Officer

Key Terms

Schedule 13G/A, Beneficially owned, Sole Dispositive Power

3 terms

Schedule 13G/A regulatory

"Amendment No. 8 ) Proto Labs Inc Common Stock"

A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.

Beneficially owned financial

"Item 4. | Ownership (a) | Amount beneficially owned: 2,497,355"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

Sole Dispositive Power regulatory

"7 | Sole Dispositive Power 2,497,355.00"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 8)

Proto Labs Inc

(Name of Issuer)

Common Stock

(Title of Class of Securities)

743713109

(CUSIP Number)

03/31/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 743713109

1

Names of Reporting Persons

DISCIPLINED GROWTH INVESTORS INC /MN

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

MINNESOTA

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 2,351,815.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 2,497,355.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,497,355.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

10.5 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Proto Labs Inc
(b)	Address of issuer's principal executive offices: 5540 Pioneer Creek, 5540 Pioneer Creek, Maple Plain, MINNESOTA, 55359.
Item 2.
(a)	Name of person filing: Disciplined Growth Investors, Inc.
(b)	Address or principal business office or, if none, residence: 150 South Fifth Street, Suite 2550 Minneapolis, MN 55402
(c)	Citizenship: Minnesota, USA
(d)	Title of class of securities: Common Stock
(e)	CUSIP No.: 743713109
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 2,497,355
(b)	Percent of class: 10.5%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 2,351,815
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 2,497,355
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

DISCIPLINED GROWTH INVESTORS INC /MN

Signature:	Peter G. Rieke
Name/Title:	Chief Operating & Compliance Officer
Date:	05/15/2026

FAQ

What stake does Disciplined Growth Investors hold in PRLB?

Disciplined Growth Investors reports beneficial ownership of 2,497,355 shares of Proto Labs common stock, equal to 10.5% of the class as reported in the amendment filed for 03/31/2026.

Does Disciplined Growth Investors have voting control over PRLB shares?

The filing shows sole voting power for 2,351,815 shares, indicating the filer can vote those shares. Shared voting power is reported as 0 in the disclosed amendment.

Is this a passive or active ownership filing for PRLB?

This is an amended Schedule 13G/A, which is used for passive investors. The amendment lists ownership and voting/dispositive powers without declaring an active acquisition intent.

When was the Schedule 13G/A amendment for PRLB signed?

The amendment was signed by Peter G. Rieke on 05/15/2026, while the ownership figures in the form are tied to 03/31/2026 as the reporting date in the excerpt.