Aspect Ratio lets you define the ratio of width to height of the container. This is a great utility for images, videos, icons and layouts that need to conform to a ratio shape as it responds. It will set the object to 100% width of the container.

class	css property	value
.aspect_8x10	aspect-ratio :	8 / 10
.aspect_1x1	aspect-ratio :	1 / 1
.aspect_2x1	aspect-ratio :	2 / 1
.aspect_4x3	aspect-ratio :	4 / 3
.aspect_3x4	aspect-ratio :	3 / 4
.aspect_3x2	aspect-ratio :	3 / 2
.aspect_16x9	aspect-ratio :	16 / 9
.aspect_21x9	aspect-ratio :	21 / 9
.aspect_4x1	aspect-ratio :	4 / 1
.aspect_leaderboard	aspect-ratio :	728 / 90
.aspect_skyscraper	aspect-ratio :	160 / 600
.aspect_bigbox	aspect-ratio :	300 / 250
.aspect_billboard	aspect-ratio :	970 / 250