Small Block: Default (breaks with anything except jumphit) and the Thowmp breaks it but will move forward.
Small and Large Block (Wider or taller): Breaks with everything except jumphit, tail attacks, and spinjump.
Giant Block (The Angry Frown Stone): Only breaks with everything except jump, Thwomp (it breaks but stops there), tail, tanooki, and spinjump. If you want to make it more interesting, modify it by programming it so that only Thwomp and Bowser can break it.
REQUIREMENTS: Use it in the SMBX38a 1.4.5 engine. and apply SMBX Magic Patcher to add it in your level