While Lenovo doesn't currently offer a WWAN option on the U350 series, the notebook comes prewired with capped off antenna leads in case you want to install your own 3G card. There is a slot for a SIM card underneath the battery for those consumers needing GSM-based WWAN options. We couldn't find any explicit "warranty void if removed" stickers inside the notebook, but there were some Lenovo-branded stickers covering the edges of the RAM, Wi-Fi card screws, and heatsink screws which may be used to indicate tampering.