Are fuse reducers available for Class T fuses?

No, fuse reducers are not available for Class T fuses.

What is the difference between Littelfuse's IDSR and FLSR ID Class RK5 fuses?

The difference is that the IDSR fuse series is the only Indicating Class RK5 fuse that is rated for 600VDC and 600VAC operation. The FLSR_ID fuse has a DC rating of 300VDC. Both the IDSR and FLSR_ID are also MSHA approved.

What is the difference between UL Class RK1 and RK5 fuses?

Class RK1 and RK5 fuses are the same physical size but Class RK1 fuses are more current-limiting than Class RK5 fuses. RK1 fuses can provide better protection because they allow less damaging energy to pass through them while opening (blowing).

Which fuse class offers better time delay?

Class RK5, RK1, and J fuses offer the most amount of time-delay. These fuses are required by UL (Underwriters Laboratories) to have a minimum of 10 seconds time delay at 500% of the fuse's rating.