The tokens.

Two tokens per window: long and short.

Long.

Gains as the index falls. At settlement it gets what short doesn't.

Short.

Gains as the index rises. If the index falls, it drifts toward zero.

What you can do.

• Hold, send or sell either token.
• Redeem one long plus one short for $1, any time.
• Keep it in a fund or wallet.
• Use it as collateral where a lender accepts it.

Example: US high yield credit.

Long is cHY and short is sHY, each dated to its window.