What oil for rear shock??

What suspension oil from Silkolene would be the best for rear shock on my Yamaha yz250 2003.??
Because Silkolene has many different oil weights (2,5wt 5wt 10wt...)!!! Or if someone can give me some informations of kayaba k2c oil (viscosity,density...) so i can compare it??

Thanks

PRO RSF RANGE

Advanced racing suspension fluids designed for the latest competition suspension systems. Integrated with low friction synthetics, anti-foam and wear-resistant additives to ensure predictable suspension performance, long seal life and silky smooth action. Used extensively by factory teams and suspension specialists in road racing and rallying competition. Provides exceptional performance in air, nitrogen and argon filled systems. Has a high viscosity index (VI), which eliminates the 'fade' experienced when shocks are required to operate at high temperatures. Available in 2.5wt, 5wt, 7.5wt, 10wt, 15wt grades, which can be individually blended to give fine-tuned suspension response.

This oil is not just for forks its for forks and shocks!!
I just need advice which would be the best of this beacause this is the only oil I can get in a day, other oils i would have to wait for a week!!!!

Here is the table of many oils i found!!

SUSP OILS

The question is if Kayaba k2c is the original oil for kayaba shocks then silkolene pro rsf 2,5wt is the closest to kayaba oil??(belray is the closest but i cant get it here)

But now i am confused because i found this site LINK and there they fill shocks with silkolene pro rsf 5wt that is much more thicker than 2,5wt??

With what oil should i go (2,5wt or 5wt)???

Thanks!

Thanks Jer!!!!!!!