Genuine Sanwa OBSC-30 round 30mm buttons with a built in microswitch, they have a short throw, positive yet silent actuation and are great for fast paced action games.
These buttons have a translucent clear rim and a solid colour plunger
They are identical in size and shape to the OBSF-30.
These buttons are a push in design with wings to hold them in place and so are suitable for 30mm holes in control panels around 2-4mm thick.
Connect these to your encoder via the 2x 2.8mm (0.110″) spade connectors on the bottom.