If you are a finger-style player with a Rickenbacker 4003, you know there is no really good place to "hang your thumb." You see many Rics with a wear spot at the corner of the pickguard, where players try to"dig in," and many Rics with the chrome cover removed from the bridge pickup to allow finger style access. Zero-Mod thumb rests were designed by a player for his own Ric 4003 basses to make them more comfortable to play, and be able to keep the "cover on" for the classic look that is a big part of this bass for many Ric fans.
This model 4003v2 is specifically designed to fit the "retro-look" pickguards that Rickenbacker began transitioning to in 2014. Please check the fit illustrations to make sure your Ric 4003 bass has this style, and not the classic 4003 pickguard which would require the Zero-Mod 4003. The look between the two guards is very similar, but the retro guard has an upper corner that is less rounded with its screw is closer to the edge.
The clear thumb rest is made out of 1/4" thick dead clear polycarbonate, and the white is top quality 1/4" acrylic. Both are precision CNC made in a machine shop here in the USA. The position and design mean NO NEW HOLES in your bass, so it's condition remains TOTALLY ORIGINAL. Both rests include two chrome pick guard screws which are slightly longer than the stock Rickenbacker screws, so you don't even change the existing screw hole size by adding this on.