PTFE sleeves The Alpha Wire PTFE sleeves are approved by AMS3653 and ASTM D 3295 and are recognised for their impressive maintainance of strength and flexibility at high temperatures. The sleeves are thoroughly insulated, allowing for continuious use up to +260 °C. As well as this, they are also waterproof, fire-retardant, not affected by mould and have excellent dielectric resistance at high frequencies.