check for available hard drive space on a Virtual machine

I'm trying to create a powershell script that will show me how much available HD space is left on each VM

So far i have a text file call machines.txt that have a list off all the VM machines, The below is my command 

$computers = Get-Content -Path "C:\dacto\machines.txt"

Invoke-Command -ComputerName $computers -ScriptBlock {

Get-WmiObject [decimal]::round((Get-WMIObject Win32_LogicalDisk | Where-Object {$_.DeviceID -eq "C:"}).freespace / 1gb)}