Two CEOs put their own cash on the line over the past week to help bolster their vision for major strategy decisions at their companies. Insider buying and selling is a metric closely tracked by many professional investors. The thinking goes that executives and board members are more willing to spend their own money buying additional shares of a company if they think the stock is undervalued. This week’s large purchases also show that insiders sometimes buy shares to help with strategic plans. The biggest buy came from RenaissanceRE CEO Kevin O’Donnell, who bought $2.5 million worth of the insurer’s stock, according to securities filings and VerityData. The purchase was part of a secondary stock offering from RenaissanceRe, according to VerityData. The move followed a recently announced deal to purchase Validus RE from AIG for nearly $3 billion. “Portfolios like this don’t come up very often. Validus has been a very capable, very strong competitor of ours,” O’Donnell said in a May 25 investor call. Another CEO putting his own money to work for corporate strategy is Masimo founder and CEO Joe Kiani. The management of the medical device company is embroiled in a contest with activist investor Politan Capital , which is pushing for two new board members at Masimo’s annual meeting in June. Masimo said Friday that it was willing to expand the board by one member and add one of the activist’s nominees. Kiani’s roughly $1 million purchase comes after he scooped up $6 million of the stock in November and December of 2022. Here is the full list of the top five insider buys of the past week, according to VerityData. 1) RenaissanceRE — O’Donnell bought $2.5 million worth of shares on May 26 as part of a secondary offering. The offering is being used to finance an acquisition of AIG’s treaty reinsurance business. 2) CNX Resources — On Tuesday, director Bernard Lanigan made his first buy at the coal company since December 2020, at a value of $2.1 million. 3) Align Tech — On Tuesday, director Kevin Dallas made his first purchase of shares of the dental products company since joining the board in 2018. He spent nearly $2 million on Align Tech stock. 4) Masimo — Kiani spent just over $1 million on Masimo stock on May 25, building on a $6 million purchase from late last year. The company is a proxy battle with activist fund Politan Capital. 5) Driven Brands — CEO Jonathan Fitzpatrick bought nearly $1 million worth of the automotive services company’s stock on Tuesday. This is Fitzpatrick’s first purchase since the company went public in January 2021. Catch weekly insider buying updates and more on CNBC’s ” Last Call ,” weekdays at 7 p.m. ET.