How to Buy Castle Biosciences, Inc. Common Stock (CSTL) Stock
Compare 13 brokers offering CSTL, check which offer overnight sessions, see options pricing, and compare fractional-share terms.
- Day range
- $34.56 – $36.08
- 52-week range
- $17.72 – $44.28
- Volume
- 297.8K
- Market cap
- $1.09B
Where to buy CSTL
13 brokers in our matrix offer CSTL. Verify availability and current fees with each broker before trading.
| Broker | Commission | Fractional | Extended | Overnight | Options | OTC access |
|---|---|---|---|---|---|---|
 Charles Schwab (thinkorswim)Review | $0 | Schwab Stock Slices, S&P 500 only, ≥ $5/slice, up to 30 at once | ~1,130 | $0.65 | Most (3/5) | |
 E*TRADE (Morgan Stanley)Review | $0 listed | ~20 | $0.65 | Most (4/5) | ||
 FidelityReview | $0 | Stocks by the Slice, 7,000+ stocks/ETFs, from $1 | $0.65 | Partial (2+0) | ||
 FirstradeReview | $0 | ~4,000+ tickers, ≥ $5 | ~1,200 | $0 | Most (4/5) | |
 Interactive BrokersReview | $0 (Lite) / per-share (Pro) | ~10,000 | per-contract pricing | Full | ||
 Merrill EdgeReview | $0 | $0.65 | Most (3/5) | |||
 MoomooReview | $0 | $0 | Limited only | |||
 Public.comReview | $0 | rebate model | Limited only | |||
 RobinhoodReview | $0 | ≥ $1 stocks, market cap ≥ $25M | ~1,134 | $0 | None | |
 SoFi Active InvestingReview | $0 | $0 | Partial (1+2) | |||
 tastytradeReview | $0 stocks | $1.00 open, $0 close (capped at $10 per leg) | Limited only | |||
 TradeStationReview | $0 listed | $0.50 / $0.60 | Most (4/5) | |||
 WebullReview | $0 | $0 | Limited only |
24-Hour / Overnight trading
These brokers run an overnight session: Charles Schwab (thinkorswim), Interactive Brokers, Robinhood, E*TRADE (Morgan Stanley), Webull, Moomoo, Firstrade. Each publishes its own list of symbols admitted to that session, and those lists are typically limited to large-cap index members. We do not track them per symbol, so check whether CSTLis on your broker’s list before planning an overnight order.
Overnight sessions route through ATSs, typically have wider spreads, accept limit orders only, and offer no guaranteed fills.
About Castle Biosciences, Inc. Common Stock
- Sector
- SERVICES-MEDICAL LABORATORIES
- Employees
- 1,002
- Headquarters
- FRIENDSWOOD, TX
- Listed
- 2019-07-25
- Market cap
- $1.09B
Frequently asked
Where can I buy Castle Biosciences, Inc. Common Stock (CSTL)?
CSTL is offered by 13 brokers in our matrix, including Charles Schwab (thinkorswim), E*TRADE (Morgan Stanley), Fidelity, Firstrade, Interactive Brokers. Compare commissions, fractional eligibility, and overnight availability in the broker matrix above.
Can I buy CSTL after hours or overnight?
Most brokers in the matrix support pre-market (4 AM–9:30 AM ET) and after-hours (4–8 PM ET) sessions. A true overnight session is offered by Charles Schwab (thinkorswim), Interactive Brokers, Robinhood, E*TRADE (Morgan Stanley), and others, but each admits only its own list of symbols — usually large-cap index members — so confirm CSTL is eligible with your broker. Overnight sessions route through ATSs with wider spreads and limit orders only.
Does Robinhood offer CSTL?
Yes. Robinhood offers CSTL as a regular exchange-listed security.
Does Fidelity offer CSTL?
Yes. Fidelity offers CSTL as a regular exchange-listed security.
Does Webull offer CSTL?
Yes. Webull offers CSTL as a regular exchange-listed security.
Is CSTL optionable?
Yes. CSTL has listed options contracts. Per-contract pricing varies by broker — see the Options column in the matrix.
Is there a tokenized version of CSTL?
Not in our current dataset. The tokenized stock universe (Kraken xStocks, Binance Alpha/Ondo, Robinhood EU, Hyperliquid HIP-3) is expanding quickly — we refresh quarterly.
Can I buy a fractional share of CSTL?
10 brokers in the matrix offer fractional shares, but each restricts the feature to its own symbol universe — Schwab to the S&P 500, Robinhood to stocks above a market-cap floor, Fidelity to a 7,000-name list. Check the Fractional column above for each broker's scope and minimum, then confirm CSTL qualifies.
Related reading
Background on the trading features that apply to CSTL.