关于TO组合密封---[请教]

最近看一本英文的工具维修手册,里面用到一种TO组合密封,相关介绍如下:

When I read a R&M Manual, I read the folling text....

1. set O-rings into groove of piston
2. heat up TO-seals in oven to 150 dc
3. take TO-seals out of oven,use high temperature resistant working gloves,stretch TO-Seals carefully and evenly and slide over piston.
4. insert piston into reform sleeve,set mounting bolt at top piston,put all into hand leverage press and push piston in. Leave TO-seal at teh smallest diameter of the reform sleeve for approximately ca.60 sec,then push piston through.
.....

I am a mechanical design engineer,I know O-ring, T-ring ect, but I don't know what is TO-seal. So could you can give any information about TO-seal.
1. What is TO-seal?
2. Where I can get more about TO-seal?
3. What is the special funtion of the TO-seal?
4. Why use the oven heat up the TO-seals?

不知道有没有国内的同行用过这种密封,很奇怪的,要先将TO圈加热,然后用成型套成型.
什么场合需要这种密封?这样密封的目的是什么?
哪里有这样的TO密封件厂家?