Most of the seats that come with your kayak, are marginal at best. Some slump down, some are just plain uncomfortable. After some research I decided on either the "Skwoosh" 20" seat, or the 2BN motion "Hi-back elite". The 2BN motion comes in black, red, blue, and camo. My IK is blue so these guys won the coin toss. The company is in Florida, and I'm in California so shipping took about a week. But, But they ship prepaid which saved me about $20.00.
The seat is listed as 18 inches high, but it was more like 19 inches by my measurement. Quality of stitching was flawless, and the back had fibreglass battens inserted for excellent support. The seat included a "pack" on the back, and holders for 2 water bottles (or beverage of choice). This seat also had a variety of adjustments to create comfort no matter the shape of your body.
Prior to this purchase, I could last about 3 hours... and the back began to ache. This seat was well worth the $99.00 I paid just for the comfort alone. And I'm the snappiest looking yakker on the river blue kayak, blue paddle, blue PFD, and now a new Blue seat. Now if I can just find blue water boots !!!!!