The inner diameter of silicone fiberglass sleeve should be measured by the required testing tool: needle gauge.
Testing methods for fiberglass casing:
1. Cut one end of the tested piece (fiberglass sleeve) flat;
2. Hold the measured piece in the left hand (fiberglass sleeve) and the needle gauge in the right hand. Cut it vertically and gently into the round hole position of the alignment part. Read it out according to the value marked on the surface of the needle gauge, and reserve two decimals for the estimated value.
3. When the needle is used up, it should be put back to its original place and kept properly.