这件外套是双层设计，外层防风，内层保暖。

This jacket has a ___two-layer design with a windproof outer shell and a warm inner lining.

这款蛋糕有两层，上面是奶油，下面是海绵蛋糕。

This cake has a ___two-layer design with cream on top and sponge at the bottom.

这个双层过滤系统先粗滤再精滤，确保水质纯净。

The ___two-layer filtration system uses coarse and fine filters to ensure water purity.