Sure,
Open this CSS file in your server:
ROOT/templates/<yourjoomlatemplate>/html/com_virtuemart/assets/css/flexibleVM2Global.css
And add this CSS rule to the bottom:
.FlexibleBrowseThumbProductInnerV2 {
min-height:307px;
}
So the product boxes will have minimum 307px height, (It is always better to do it with min-height rule, instead of fixed "height" rule.... in case you might have a product in the future with 3 or 4 lines title.
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