Constantin Ionel Stefan is CTO at Amprius Technologies, Inc. (AMPX). They have made 15 open-market trades across 1 company since 2023, most recently 2026-08-21.
CIK 0001940928
Unrated. We grade insiders only on stock they chose to buy on the open market. Grants, option exercises and vesting say nothing about timing, so they don't count — which is why someone can file often and still have no grade. It isn't a bad sign: unrated buys beat every graded tier below A.
0 open-market purchases, against 15 sales. Too few scored purchases to measure a record yet.
| Ticker | Shares | Value |
|---|---|---|
| AMPX | 771,629 | $5.9M |
Shares reported on the most recent Form 4, priced at the 2026-08-25 close.
Counted per filing, not per execution lot — a purchase filled in several tranches is one decision.
| Ticker | Type | Traded | Filed | Price | Value | 7d Stock | 30d Stock | 90d Stock |
|---|---|---|---|---|---|---|---|---|
| AMPX | SELL | 2026-08-21 | 2026-08-25 | $10.34 | $307K | -4.0% | -5.7% | — |
| AMPX | SELL | 2026-05-27 | 2026-05-28 | $17.19 | $55K | -15.1% | -34.0% | -50.3% |
| AMPX | SELL | 2026-05-21 | 2026-05-26 | $14.79 | $426K | +12.5% | -28.3% | -43.7% |
| AMPX | SELL | 2026-02-23 | 2026-02-24 | $10.16 | $258K | +48.9% | +56.4% | +62.3% |
| AMPX | SELL | 2026-01-28 | 2026-01-30 | $12.00 | $476K | -10.3% | -6.5% | +70.1% |
| AMPX | SELL | 2026-01-21 | 2026-01-23 | $12.03 | $6.8M | +11.7% | -8.1% | +95.8% |
| AMPX | SELL | 2025-12-11 | 2025-12-15 | $10.51 | $4.2M | -16.5% | +4.6% | +88.8% |
| AMPX | SELL | 2025-11-21 | 2025-11-25 | $10.08 | $504K | +8.1% | -24.3% | -6.6% |
| AMPX | SELL | 2025-08-21 | 2025-08-25 | $6.82 | $261K | -6.2% | +46.3% | +42.5% |
| AMPX | SELL | 2025-05-21 | 2025-05-23 | $2.43 | $49K | -9.0% | +19.4% | +134.9% |
| AMPX | SELL | 2025-02-21 | 2025-02-24 | $3.13 | $28K | -28.9% | +9.3% | +0.4% |
| AMPX | SELL | 2024-11-21 | 2024-11-22 | $1.96 | $17K | +4.5% | -5.0% | +66.0% |
| AMPX | SELL | 2024-08-21 | 2024-08-22 | $1.04 | $9K | -13.6% | +7.6% | +83.8% |
| AMPX | SELL | 2024-05-21 | 2024-05-24 | $1.34 | $13K | -9.4% | -16.1% | -28.2% |
| AMPX | SELL | 2023-09-14 | 2023-09-18 | $3.76 | $601K | -8.0% | -30.2% | -27.4% |
Grouped by shared companies and similar filing behaviour. This is a similarity measure, not a ranking or a performance signal.