RF bonding applications a stainless-steel die is precisely heated using RF energy. The stainless-steel dies are sized and designed for each specific application. Heat shrink is not typically utilized for RF applications, but the tooling cannot provide radial compression similar to heatsink. For this reason, RF heated dies are not used for most lap joints, but they are the preferred technology for butt welds. PTFE sleeves can be incorporated into the die to eliminate sticking and increase bond strength.