saddlecloth and number

Question
What size is the saddle cloth used to signify each horses post position. How much does it weigh? What are they made out of?

Answer
The range of sizes for saddle clothes can and do vary but to me they are usually sized around a range of 38" x 22", but remember the size do vary on both sides of the measuring stick.
Now, when it come to Stake Races horse will have their names embroidered on the saddle cloth in addition to the number.
The weight of the saddle cloth is about the weight of a t-shirt, which is basically no-existent to to the horse. These are very light as not to affect the running action of the horse within the race.
They are made out of cloth material or I've seen more of a polyester type of material.
Overall the size & material used is determined by the jurisdiction & producers of the particular saddle cloth.
I hope this helps to answer your question.