缓冲（预设结果）ETF

通过期权构建的基金，以放弃一定上行空间换取特定周期内的下行保护。

Buffer ETFs use options packages to offer a defined outcome over an outcome period (usually 12 months): they absorb the first X% of the index's loss (the buffer) in exchange for capping your upside at Y%. Both numbers are set on the period's start date.

The defined outcome only applies if you buy on day one and hold to the period's end. Buy mid-period and your effective buffer and cap differ from the headline; issuers publish 'remaining buffer/cap' figures daily for this reason.

These funds hold options, not stocks, so they pay little or no dividend income, and the cap means strong bull markets are largely given away. They are a risk-shaping tool with real, quantifiable trade-offs printed in the prospectus.