Unlike eeSilk and eeSilk+ Seatposts, the eeSilk Stem elastomers were developed based on rider preference and varying terrain rather than rider weight.
We chose not to do a weight rating system for elastomers because there are many factors that affect how they feel and perform such as rider weight, stem length, bike fit, etc. Therefore, recommending using X elastomer for a 200lb person riding an 80mm stem and another 200lb person riding a 100mm stem would not be ideal. Even if you were to put the medium elastomer in an 80mm stem, it would feel firmer than if placed in a 100mm stem.
This is where the single bolt external elastomer change comes in handy. It will allow you to dial in the feel you want and even switch out elastomers depending on the intended ride that day. We recommend riding the installed elastomer to get a base of what you prefer and trying a softer or harder one accordingly. We also offer additional elastomers (other than the three that came with your stem) available separately.