Flexbox: How to Combine percent, pixels and remaining height on columns?

I'm building basic grid system and need to combine height of flex-items described in different size units, which are %, px and remaining space.

html:

<div class="grid">
  <div class="block" style="flex-basis: 50px;">50px</div>
  <div class="block" style="flex-basis: 25%;">25%</div>
  <div class="block">stretch to remaining space?</div>
  <div class="block" style="flex-basis: 50px;">50px</div>
</div>

css:

html,body,.grid {
  height: 100%;
  padding: 0;
  margin: 0;
}
.grid {
  width: 300px;
  background: #aaa;
  display: flex;
  flex-direction: column;
  justify-content: flex-start;

}
.block {
  outline: solid 1px black;
  flex-grow: 0; // remove growing proportion
  flex-shrink: 0; // remove shrinking proportion
}

working example: http://codepen.io/antraxis/pen/zxwgEo

Use the flex-grow parameter (the first one in the flex shorthand property) :

* { margin: 0; box-sizing: border-box; }

.grid {
  height: 100dvh;
  background: #aaa;
  display: flex;
  flex-direction: column;
}

.block {
  outline: solid 1px black;
}

.a {
  flex: 0 0 50px;
}

.b {
  flex: 0 0 15%;
}

.c {
  flex: 1 0 0;
}

<div class="grid">
  <div class="block a">block height 50px</div>
  <div class="block b">block height 15%</div>
  <div class="block c">block height *</div>
  <div class="block a">block height 50px</div>
</div>

codepen