Toilet Seat Measurements Guide, Elongated vs. Round
Elongated seat is oval shaped seats which is about 2" longer than a round bowl and often found to be more comfortable but in small bathroom, a round bowl can save space.
Toilet Type Guide, 1PC vs. 2PC
One piece toilet has the toilet housed in one complete unit where two piece toilets has a separate bowl and tank. Offered Bio Bidet seat models are designed to fit all 2 piece toilets and most of 1 piece toilets. Only exception will be rare types of one piece toilets with severe French curves where toilet tank connects to the base of toilet such as type C below.
TYPE A and B : YES , TYPY C : NO