William Blair Investment Management
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William Blair Investment Management’s Mirion Technologies MIR Stock Holding History

William Blair Investment Management’s Portfolio MIR Stock Details MIR Fund Activity
Bought
Maintained
Sold
Quarter Market Value Status Shares Change in
Stake 		Trade Value Portfolio Weight Portfolio Position
2025
Q3 		– Sell
-1,005,847
Closed -$21.7M – 435
2025
Q2 		$21.7M Sell
1,005,847
-725,544
-42% -$12.5M 0.06% 276
2025
Q1 		$25.1M Sell
1,731,391
-1,309,625
-43% -$20.6M 0.07% 260
2024
Q4 		$53.1M Buy
+3,041,016
New +$47.2M 0.13% 148

Other funds holding MIR

BlackRock
BlackRock New York $5.72T AUM 30.48% 1-Year Est. Return
Vanguard Group
Vanguard Group Malvern, Pennsylvania $6.9T AUM 27.45% 1-Year Est. Return
T. Rowe Price Investment Management
T. Rowe Price Investment Management Baltimore, Maryland $145B AUM 22.78% 1-Year Est. Return
Fidelity Investments
Fidelity Investments Boston, Massachusetts $1.9T AUM 41.92% 1-Year Est. Return
State Street
State Street Boston, Massachusetts $2.9T AUM 29.55% 1-Year Est. Return
CLG
Cooperman Leon G $3.05B AUM 42.78% 1-Year Est. Return
Janus Henderson Group
Janus Henderson Group London, United Kingdom $209B AUM 37.72% 1-Year Est. Return
Dimensional Fund Advisors
Dimensional Fund Advisors Austin, Texas $481B AUM 30.42% 1-Year Est. Return
Geode Capital Management
Geode Capital Management Boston, Massachusetts $1.61T AUM 30.72% 1-Year Est. Return
Massachusetts Financial Services
Massachusetts Financial Services Boston, Massachusetts $298B AUM 21.96% 1-Year Est. Return

William Blair Investment Management's MIR Position: Q3 2025 in Review

William Blair Investment Management sold out of Mirion Technologies (MIR) in Q3 2025, closing a stake of 1,005,847 shares — an estimated $21.7M sold.

William Blair Investment Management first reported a position in MIR in Q4 2024 and held it in 3 quarters. The position peaked at $53.1M in Q4 2024. 341 funds tracked by Wall St. Rank hold MIR as of Q3 2025.

  • William Blair Investment Management reported no remaining Mirion Technologies position as of Q3 2025 after selling out during the quarter.
  • William Blair Investment Management sold 1,005,847 Mirion Technologies shares in Q3 2025, an estimated $21.7M.
  • William Blair Investment Management first reported a position in Mirion Technologies in Q4 2024 and held it in 3 quarters.
  • William Blair Investment Management's Mirion Technologies position peaked at $53.1M in Q4 2024.
  • 341 funds tracked by Wall St. Rank held Mirion Technologies as of Q3 2025.

Based on William Blair Investment Management's 13F filing for Q3 2025, filed 12 Nov 2025.