The spacer slots run the length of the Rega headshell slots (shown in the last image).
Michell Technoweight Counterweight Upgrade - Rega Tonearm Hifi Turntables
Phono Cartridge Spacer Shims VTA Kit for Turntable Thorens Rega Linn, UK made
VTA VERTICAL ADJUSTER + LOCK NUT FITS REGA TONE ARM RB250 RB300 RB600 MICHELL
Rega VTA Adjustment Spacer Set 1-12mm for 3 point mount RB220, 330, 251, 303 etc
Rega Planar RB250 / RB300 Tonearm Rewire Cable, Pure Silver 5N Litz Wires 400mm
Rega R200 Tonearm Bias Belt Replacement Anti Skate Belt