Welcome to TG WasteWater
A few years back many counties began passing laws that require every septic system to have 2 layers of protection per septic tank riser hole. The reason for this was so that the hole into the septic tank would be covered up even if the septic tank lid was removed. This prevents anyone (especially children) from falling into the septic system.
The Tuff-Tite safety pans fit in any Tuff-Tite riser with tabs. (all Tuf-Tite risers sold by TGWasteWater include the tabs) They screw in to the 4 tabs on each riser. Each safety pan includes 4 stainless steel screws to attach them to the riser. (Stainless screws are used to prevent corrosion)
If your current septic system does not include safety pans we highly recommend adding them. Not only does it improve safety but it may be the law in your area.