There's another thread currently active, asking almost this same question. Each type slide and each manufacturer installs a bit differently.
I also don't see that you listed your R/V make/model nor do I see it in your profile.
Here is my reply in that thread...
Looking at different slides (Schwintek, Lippert, etc) and manufacturing divisions (Rockwood, Coachmen, etc) over the last many years, they all seem to use a bit different seal.
You'll likely need to determine what yours is and then locate a seal that matches. There are many seal sellers online that sell by the foot.
2016 Flagstaff 8529IKBS Diamond Package 5th Wheel-Goodyear Endurance Tires
2017 Ford F-Series SCREW 4x4 - Factory Puck B&W Companion
TST Tire Monitor w/Repeater - Sinemate 3500w Gen.
Days Camped: '18=51 ☼ '19=58 ☼ '20=110 ☼ '21=21