suspension question

[cr4sh_27]

so im ordering king headz parts for my losi 8 and i come across this part:
KP-220-2x2 - Toe/Anti-squat Pivot Brace - T2/A2
as you all know, my buggy was bout as an rtr but now is in the finall pro conversion stages.

so before i order these hinge pin braces, i have a few questions.

1) i dont understand exactly what anti-squat does or how it works
2) how do i decide which one to get...there are a couple different ones

can anyone help? right now i have the stock braces that have the crappy plastic covers on them. so i want to upgrade, but dont wanna grab the wrong braces.

thanks