How to Buy Castle Biosciences, Inc. Common Stock (CSTL) Stock

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

CSTL may be eligible for overnight trading via Charles Schwab (thinkorswim), Interactive Brokers, Robinhood, E*TRADE (Morgan Stanley), Webull, Moomoo, Firstrade. Each broker maintains its own eligibility list — confirm before placing an order.

About Castle Biosciences, Inc. Common Stock

Castle Biosciences Inc is a molecular diagnostics company. The group provides test solutions for the diagnosis and treatment of dermatologic cancers, Barrett's esophagus (BE), and uveal melanoma. The product portfolio of the company includes DecisionDx-Melanoma, a risk stratification gene expression profile (GEP) test; DecisionDx-SCC, a risk stratification test for cutaneous squamous cell carcinoma; MyPath Melanoma, a diagnostic GEP test for use in patients with difficult-to-diagnose melanocytic lesions; and TissueCypher, a test to predict future development of progression of high-grade dysplasia and/or esophageal cancer. The company derives revenues through the delivery of test reports for its molecular diagnostic tests.

Sector

SERVICES-MEDICAL LABORATORIES

Employees

942

Headquarters

FRIENDSWOOD, TX

Listed

2019-07-25

Market cap

$607.51M

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?

Yes. CSTL is on the 24-hour eligibility list for Charles Schwab (thinkorswim), Interactive Brokers, Robinhood, E*TRADE (Morgan Stanley), and others. 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?

Yes. Multiple brokers in the matrix support fractional shares for CSTL — see the Fractional column above for per-broker eligibility and minimums.