|Deluxe factory replacement screw-in rear velocity adjuster for mechanical Spyder & Java markers (except VS series). Fits all 09 Victor, Aggressor, Sonix, Xtra and all models that utilize a screw-in rear cap. Original List price was $19.95! Replaces the rear end cap and includes the integrated spring guide which prevents spring kinking (which can cause velocity problems). Flush design requires a small Allen wrench to adjust the velocity. This makes this unit field and tournament legal! Eliminates the need to cut your main spring or disassemble your gun. Adjustable from 180 fps - 300 fps. A very handy drop in accessory! All black anodized aluminum.