yes they are insured but up to $250k only per account.
Our custodial accounts have been established in a manner to make pass-through FDIC insurance available up to the per-depositor coverage limit then in place (currently $250,000 per individual).
So make sure your deposit doesn't exceed their insurance limit. It’s always wise not to keep your Bitcoin on an exchange since you don’t own the keys. Exchanges are mostly for trading purposes only, so as long as your capital isn’t too large, your funds should be safe as long as they don't exceed the coverage ceiling.