a register 52 thus air is efficiently delivered from the furnace 1 to each register 52 by traveling through the duct 3 duct opening 50 straight 5 or 90 degree 6 takeoffs flexible 10 or rigid 7 pipes and into a torpedo 11 register 13 or straight 14 boot attached to the register 52 fig2 illustrates the 90 degree regular plastic register boot 13 in greater detail the regular plastic register boot 13 includes a unitary body 15 of plastic the plastic is preferably an injection molded thermoplastic the unitary body 15 has a substantially circular first opening 23 for connecting to a flexible 10 or rigid 7 pipe the unitary body 15 also has a substantially rectangular second opening 20 for connection to a register 52 thus air travels from the flexible 10 or rigid 7 pipe and through the first opening 23 the unitary body 15 the second opening 20 and to the register 52 due to the unitary plastic construction the register boot is seamless thereby preventing loss of air within the register boot itself thus the unitary plastic is generally advantageous over a multi piece construction a multi piece construction would also tend to increase the labor required in installing the register boot the unitary body 15 has integrated collars 16 and 17 for fitting the plastic register boot 13 to different sizes of diameter flexible 10 and rigid 7 pipe for example the collar 16 is preferably adapted to fit 6 inch diameter flexible 10 or rigid 7 pipe while the collar 17 is preferably adapted to fit 7 inch diameter flexible 10 or rigid 7 pipe because the unitary body is of a plastic.