found these on Ebay and was wondering if they would be good to use for the raiser in the RMH drum.

https://www.ebay.com/itm/Kaowool-Sleeve-Insulation-High-Temperature-Forges-Kilns-Black-Smithing/162969717526?hash=item25f1c08b16:g:GJYAAOSwR4JalFc-

Not very well .  9" is too large  for an 8" system. At $48.70 for each 12" piece it would be a spendy riser... mine is 52" tall in an 8" system...  so $243.50 for a 48" riser... not cost effective even if they combine shipping.
I build my risers any height I need, using fireclay/perlite, an 8" id sonotube and a 16 gallon grease barrel as an outer form...  total cost might be $40.00 .....  "broaudio" on you tube will explain how to cast risers.

Thanks Thomas. Ive seen the method you mentioned.  How well do they withstand the heat and how long before it would need replacement.

Short answer , A LONG TIME.  My first one lasted 3 years ,  what failed was the 16 gal barrel got rusty at the bottom edge and tilted, which caused the riser to crack. If not for that happening that riser would still be in use today.  One of the nice features of building a riser this way is the ability to uncob and lift it off of a core if (or when) you go in to modify your core unit.
Of course if you can afford it the "newest... best.." thing in RMH's is 1" thick ceramic fiber board or tubing being used for cores (other than the feed tube) and to build risers.  The downside is the cost...  I haven't spent the money on ceramic fiber boards yet myself,  but the performance reports are so good that they will  be used at my home sometime in the future.

So what would be the high temperatures reached in a RMH?

Inside the riser they say 1500-1800 F or more in a batch box. Top of barrel at my rmh has been seen at  1100 F Normal barrel top is 800 F exhaust pipe where popping out of the mass is 130 F  Top of stack same thing 130 F

Inside the riser of a batch box 1050º C (1920º F) is quite normal once at operating temperature. Theoretical maximum of an atmospheric-aspirated wood burning device is 1200º C which is the equivalent of 2190º F. I have one recorded figure of 1172º C (2140º F), very close to that maximum.

Current Guiness world record for a wood fired kiln is 1563C(2845F). It took 3 days!!!

http://www.guinnessworldrecords.com/world-records/428387-highest-temperature-in-a-wood-fired-kiln

I used one of these in my 6" system, the one mentioned in my "Burning perlite?" thread. 36" Insulated Double Wall Stainless Chimney Pipe - Lowes.com

Every year I checked it when I opened it up for cleaning, and saw no damage. But for $90 or so it wouldn't be a huge deal (for most people) to replace it every year.

For my PvdB 6" batchbox I went with an IFB (Insulated Fire Brick) heat riser (2600° F. rating) sourced from a local Harbison Walker refractories outlet (many locations scattered around the US). Anyway, three seasons down and the heat riser is going strong, and is expected to last for a good many years yet to come. It took three cases of IFB for the heat riser construction, and the cost at that time was in the range of $120.

i'm thinking i can use these for the outside form of the stack and use a high quality refactory cement lining. at $15 a piece its worth experimenting with