Parts manual and schematics for Jet Rocket.
We also have similar copies for many other SEGA games of that period including Moto Polo, Basketball, and others.
The shipping module can't handle pricing for envelopes - so it assumes a box and charges accordingly! We refund the difference depending on the actual cost plus our handling fee of $5.
Shipping an envelope (maximum dimensions are 38cm x 27cm x 2cm or 15in x 10.5in x 3/4in) to the USA costs us 3.80 if it weighs 200 grams or less, and $7.60 up to 500 gms (about a pound). So adding our handling fee gives us $8.80 or $12.60 and we then refund the difference to you.
International envelopes cost $7.60 for up too 200 gms, and 15.20 for up to 500gms.