Our drop link is made from the original Royal Enfield OEM part, it weights 385g.
The 4cm version will lower the bike by 4 cm or 1.57 inch.
With a extended drop link the behavior of your bike will change. You will touch the ground earlier when leaning into curves and going through holes in the road the suspension will max out earlier too. In normal riding conditions, especially solo, that is no big deal but if you travel with pillion and/or lots of luggage the effect is quite pronounced.
To level the lowering of the rear part you can also lower the fork by 2cm, just loosen the 4 screws on both sides and push the fork up.
Here you can watch us making the extension: