Got a Rockshox Super Deluxe Coil shock? Want to change the stroke length? You'll need one of these, as follows:
55/65/75mm stroke - no spacer
52.5/62.5/72.5mm stroke - 2.5mm spacer
50/60/70mm stroke - 5mm spacer
47.5/57.5/67/5mm stroke - 7.5mm spacer
If your shock is the new 2023 model, with hydraulic bottom out control, then you'll need a HBO Bolt too.
CNC'd out of durable Delrin® acetal homopolymer, these are a direct replacement for Rockshox spacers.