Aftermarket sells LOTS of stuff......some good, some OK and SOME JUST TO GET YOUR MONIES
Folks buy/use them due to 'marketing' hype....period.
Slideouts are 'self-supporting' when extended.
IF slideout 'supports' were needed don't you think RV MFG would supply them, require them, recommend them during the 'warranty' period to prevent issues that they would have to fix/repair ???
NO...slideouts do NOT need or require supports.
Using them CAN cause damage to slideouts due to the UPWARD pressure that slideouts are not designed for.
Use them at YOUR own risk.
The following is a statement directly from an RV MFGs owners manual
Additional support jacks are not needed under the slideout.
Damage can occur to your slideout room from improper use of aftermarket support jacks.